class IO::Special

Path to Special I/O device

class IO::Special does IO { }

Used as a $.path attribute in special standard input and output handles $*IN, $*OUT and $*ERR. Provides abridged interface of IO::Handle, mostly file tests and stringification.


method new

method new(:$!what!)

Takes a single required attribute what. It is unlikely that you will ever need to construct one of these objects yourself.

attribute what

say $*OUT.path.what# OUTPUT: «<STDOUT>␤» 

Returns one of the strings '<STDIN>', '<STDOUT>', or '<STDERR>', specifying the type of the special IO device.

method WHICH

method WHICH(IO::Special:D: --> Str)

This returns a string that identifies the object.

method Str

method Str(IO::Special:D:)

This returns '<STDIN>', '<STDOUT>', or '<STDERR>' as appropriate.

method IO

method IO(IO::Special:D: --> IO::Special)

Returns the invocant.

method e

method e(IO::Special:D: --> Bool)

The 'exists' file test operator, always returns True.

method d

method d(IO::Special:D: --> Bool)

The 'directory' file test operator, always returns False.

method f

method f(IO::Special:D: --> Bool)

The 'file' file test operator, always returns False.

method s

method s(IO::Special:D: --> Int)

The 'size' file test operator, always returns 0.

method l

method l(IO::Special:D: --> Bool)

The 'symbolic links' file test operator, always returns False.

method r

method r(IO::Special:D: --> Bool)

The 'read access' file test operator, returns True if this is the standard input handle, False otherwise.

method w

method w(IO::Special:D: --> Bool)

The 'write access' file test operator, returns True if this is the standard output or standard error handle, False if it is the standard input.

method x

method x(IO::Special:D: --> Bool)

The 'execute access' file test operator, always returns False.

method modified

method modified(IO::Special:D: --> Instant)

The last modified time always returns an Instant type object.

method accessed

method accessed(IO::Special:D: --> Instant)

The last accessed time always returns an Instant type object.

method changed

method changed(IO::Special:D: --> Instant)

The last changed time always returns an Instant type object.

method mode

method mode(IO::Special:D: --> Nil)

The mode always returns Nil

Type Graph

Type relations for IO::Special
perl6-type-graph IO::Special IO::Special Any Any IO::Special->Any IO IO IO::Special->IO Mu Mu Any->Mu

Stand-alone image: vector

Routines supplied by role IO

IO::Special does role IO, which provides the following methods:

(IO) sub mkdir

Defined as:

sub    mkdir(IO() $pathInt() $mode = 0o777 --> IO::Path:D)

Creates a new directory; see mode for explanation and valid values for $mode. Returns the IO::Path object pointing to the newly created directory on success; fails with X::IO::Mkdir if directory cannot be created.

Also creates parent directories, as needed (similar to *nix utility mkdir with -p option); that is, mkdir "foo/bar/ber/meow" will create foo, foo/bar, and foo/bar/ber directories if they do not exist, as well as foo/bar/ber/meow.

(IO) sub chdir

Defined as:

sub chdir(IO() $path:$d = True:$r:$w:$x --> IO::Path:D)

Changes value of $*CWD variable to the provided $path, optionally ensuring the new path passes several file tests. NOTE: that this routine does NOT alter the process's current directory (see &*chdir).

Returns IO::Path representing new $*CWD on success. On failure, returns Failure and leaves $*CWD untouched. The $path can be any object with an IO method that returns an IO::Path object. The available file tests are:

  • :d — check .d returns True

  • :r — check .r returns True

  • :w — check .w returns True

  • :x — check .x returns True

  • By default, only :d test is performed.

    chdir         '/tmp'# change $*CWD to '/tmp' and check its .d is True 
    chdir :r:w'/tmp'# … check its .r and .w are True 
    chdir '/not-there';   # returns Failure 

    Note that the following construct is a mistake:

    my $*CWD = chdir '/tmp/';

    Use indir instead.

    (IO) sub &*chdir

    Defined as:

    PROCESS:<&chdir> = sub (IO() $path --> IO::Path:D)

    Changes value of $*CWD variable to the provided $path and sets the process's current directory to the value of $path.absolute. NOTE: that in most cases, you want to use chdir routine instead.

    Returns IO::Path representing new $*CWD on success. On failure, returns Failure and leaves $*CWD untouched. The $path can be any object with an IO method that returns an IO::Path object.

    Note that unlike regular chdir, there are no arguments to specify which file tests to perform.

    &*chdir('/tmp');  # change $*CWD and process's current directory to '/tmp' 
    &*chdir('/not-there'); # returns Failure 

    Note that the following construct is a mistake:

    my $*CWD = &*chdir('/tmp');

    Use the following, instead; or see indir if you do not need to change process's current directory:

    temp $*CWD;

    (IO) sub chmod

    Defined as:

    sub chmod(Int() $mode*@filenames --> List)

    Coerces all @filenames to IO::Path and calls IO::Path.chmod with $mode on them. Returns a List containing a subset of @filenames for which chmod was successfully executed.

    chmod 0o755, <myfile1  myfile2># make two files executable by the owner 

    (IO) sub indir

    Defined as:

    sub indir(IO() $path&code:$d = True:$r:$w:$x --> Mu)

    Takes Callable &code and executes it after locally (to &code) changing $*CWD variable to an IO::Path object based on $path, optionally ensuring the new path passes several file tests. If $path is relative, it will be turned into an absolute path, even if an IO::Path object was given. NOTE: that this routine does NOT alter the process's current directory (see &*chdir). The $*CWD outside of the &code is not affected, even if &code explicitly assigns a new value to $*CWD.

    Returns the return value of &code on success. On failure to successfully change $*CWD, returns Failure. WARNING: keep in mind that lazily evaluated things might end up NOT having the $*CWD set by indir in their dynamic scope by the time they're actually evaluated. Either ensure the generators have their $*CWD set or eagerly evaluate them before returning the results from indir:

    say indir("/tmp"{
        gather { take ".".IO }
    }.CWD# OUTPUT: «(/home/camelia)␤» 
    say indir("/tmp"{
        eager gather { take ".".IO }
    }.CWD# OUTPUT: «(/tmp)␤» 
    say indir("/tmp"{
        my $cwd = $*CWD;
        gather { temp $*CWD = $cwdtake ".".IO }
    }.CWD# OUTPUT: «(/tmp)␤» 

    The routine's $path argument can be any object with an IO method that returns an IO::Path object. The available file tests are:

  • :d — check .d returns True

  • :r — check .r returns True

  • :w — check .w returns True

  • :x — check .x returns True

  • By default, only :d test is performed.

    say $*CWD;                   # OUTPUT: «"/home/camelia".IO␤» 
    indir '/tmp'{ say $*CWD }# OUTPUT: «"/tmp".IO␤» 
    say $*CWD;                   # OUTPUT: «"/home/camelia".IO␤» 
    indir '/not-there'{;};     # returns Failure; path does not exist 

    (IO) sub print

    Defined as:

    multi sub print(**@args --> True)
    multi sub print(Junction:D --> True)

    Prints the given text on standard output (the $*OUT file handle), coercing non-Str objects to Str by calling .Str method. Junction arguments autothread and the order of printed strings is not guaranteed.

    print "Hi there!\n";   # OUTPUT: «Hi there!␤» 
    print "Hi there!";     # OUTPUT: «Hi there!» 
    print [123];       # OUTPUT: «1 2 3» 

    To print text and include the trailing newline, use put.

    (IO) sub put

    Defined as:

    multi sub put(**@args --> True)
    multi sub put(Junction:D --> True)

    Same as print, except appends $* (a newline, by default) at the end. Junction arguments autothread and the order of printed strings is not guaranteed.

    put "Hi there!\n";   # OUTPUT: «Hi there!␤␤» 
    put "Hi there!";     # OUTPUT: «Hi there!␤» 
    put [123];       # OUTPUT: «1 2 3␤» 

    (IO) sub say

    Defined as:

    multi sub say(**@args --> True)

    Prints the "gist" of given objects. Same as put, except uses .gist method to obtain string representation of the object.

    NOTE: the .gist method of some objects, such as Lists, returns only partial information about the object (hence the "gist"). If you mean to print textual information, you most likely want to use put instead.

    say Range;        # OUTPUT: «(Range)␤» 
    say class Foo {}# OUTPUT: «(Foo)␤» 
    say 'I ♥ Perl6';  # OUTPUT: «I ♥ Perl6␤» 
    say 1..Inf;       # OUTPUT: «1..Inf␤» 

    (IO) routine note

    Defined as:

    method note(Mu: -->Bool:D)
    multi sub note(            --> Bool:D)
    multi sub note(Str:D $note --> Bool:D)
    multi sub note(**@args     --> Bool:D)

    Like say, except prints output to $*ERR handle (STDERR). If no arguments are given to subroutine forms, will use string "Noted".

    note;       # STDERR OUTPUT: «Noted␤» 
    note 'foo'# STDERR OUTPUT: «foo␤» 
    note 1..*;  # STDERR OUTPUT: «1..Inf␤» 

    (IO) sub prompt

    multi prompt()
    multi prompt($msg)

    Prints $msg to $*OUT handle, if $msg was provided, then gets a line of input from $*IN handle. By default, this is equivalent to printing $msg to STDOUT, reading a line from STDIN, removing the trailing new line, and returning the resultant string.

    my $name = prompt "What's your name? ";
    say "Hi, $name! Nice to meet you!";

    (IO) sub open

    multi sub open(IO() $path|args --> IO::Handle:D)

    Creates a handle with the given $path, and calls, passing any of the remaining arguments to it. Note that IO::Path type provides numerous methods for reading and writing from files, so in many common cases you do not need to open files or deal with IO::Handle type directly.

    my $fh = open :w'/tmp/some-file.txt';
    $fh.say: 'I ♥ writing Perl code';
    $fh = open '/tmp/some-file.txt';
    print $fh.readchars: 4;
    $ 7SeekFromCurrent;
    say $fh.readchars: 4;
    # OUTPUT: «I ♥ Perl␤» 

    (IO) sub slurp

    Slurps the contents of the entire file into a Str (or Buf if :bin). Accepts :bin and :enc optional named parameters, with the same meaning as open(). The routine will fail if the file does not exist, or is a directory.

    # read entire file as (Unicode) Str 
    my $text_contents   = slurp "path/to/file";
    # read entire file as Latin1 Str 
    my $text_contents   = slurp "path/to/file"enc => "latin1";
    # read entire file as Buf 
    my $binary_contents = slurp "path/to/file":bin;

    (IO) sub spurt

    Defined as:

    multi spurt(IO() $path|c)

    The $path can be any object with an IO method that returns an IO::Path object. Calls IO::Path.spurt on the $path, forwarding any of the remaining arguments.


  • :enc

  • The encoding with which the contents will be written.

  • :bin

  • Open the file in binary mode.

  • :append

  • Boolean indicating whether to append to a (potentially) existing file. If the file did not exist yet, it will be created. Defaults to False.

  • :createonly

  • Boolean indicating whether to fail if the file already exists. Defaults to False.


    # write directly to a file 
    spurt 'path/to/file''default text, directly written';
    # write directly with a non-Unicode encoding 
    spurt 'path/to/latin1_file''latin1 text: äöüß':enc<latin1>;
    spurt 'file-that-already-exists''some text';           # overwrite file's contents: 
    spurt 'file-that-already-exists'' new text':append;  # append to file's contents: 
    say slurp 'file-that-already-exists';                    # OUTPUT: «some text new text␤» 
    # fail when writing to a pre-existing file 
    spurt 'file-that-already-exists''new text':createonly;
    # OUTPUT: «Failed to open file /home/camelia/file-that-already-exists: file already exists …» 

    (IO) sub run

    sub run(*@args ($*@) --> Proc)

    Runs an external command without involving a shell and returns a Proc object.

    run 'touch''>foo.txt'# Create a file named >foo.txt 
    run <<rm >foo.txt>># Another way to use run, using word quoting for the 
                         # arguments 

    If you want to pass some variables you can still use < >, but try to avoid using « » as it will do word splitting if you forget to quote variables:

    my $file = --my arbitrary filename;
    run touch--$file;  # RIGHT 
    run <touch -->$file;     # RIGHT 
    run «touch -- "$file"»;    # RIGHT but WRONG if you forget quotes 
    run «touch -- $file»;      # WRONG; touches ‘--my’, ‘arbitrary’ and ‘filename’ 
    run touch$file;        # WRONG; error from `touch` 
    run «touch "$file"»;       # WRONG; error from `touch` 

    Note that -- is required for many programs to disambiguate between command-line arguments and filenames that begin with hyphens.

    A sunk Proc object for a process that exited unsuccessfully will throw. If you wish to ignore such failures, simply use run in non-sink context:

    run 'false';     # SUNK! Will throw 
    run('false').so# OK. Evaluates Proc in Bool context; no sinking 

    To capture output or error you can use the :out or :err arguments respectively:

    my $proc = run 'echo''Perl 6 is Great!':out:err;
    $proc.out.slurp(:close).say# OUTPUT: «Perl 6 is Great!␤» 
    $proc.err.slurp(:close).say# OUTPUT: «␤» 

    See Proc and Proc::Async for more details.

    (IO) sub shell

    sub shell($cmd --> Proc)

    Runs a command through the system shell. All shell meta characters are interpreted by the shell, including pipes, redirects, environment variable substitutions and so on. Shell escapes are a severe security concern and can cause confusion with unusual file names. Use run if you want to be safe.

    The return value is of type Proc.

    shell 'ls -lR | gzip -9 > ls-lR.gz';

    See Proc for more details, for example on how to capture output.

    Routines supplied by class Any

    IO::Special inherits from class Any, which provides the following methods:

    (Any) method ACCEPTS

    Defined as:

    multi method ACCEPTS(Any:D: Mu $other)



    Returns True if $other === self (i.e. it checks object identity).

    Many built-in types override this for more specific comparisons

    (Any) method any

    Defined as:

    method any(--> Junction:D)

    Interprets the invocant as a list and creates an any-Junction from it.

    say so 2 == <1 2 3>.any;        # OUTPUT: «True␤» 
    say so 5 == <1 2 3>.any;        # OUTPUT: «False␤» 

    (Any) method all

    Defined as:

    method all(--> Junction:D)

    Interprets the invocant as a list and creates an all-Junction from it.

    say so 1 < <2 3 4>.all;         # OUTPUT: «True␤» 
    say so 3 < <2 3 4>.all;         # OUTPUT: «False␤» 

    (Any) method one

    Defined as:

    method one(--> Junction:D)

    Interprets the invocant as a list and creates a one-Junction from it.

    say so 1 == (123).one;      # OUTPUT: «True␤» 
    say so 1 == (121).one;      # OUTPUT: «False␤» 

    (Any) method none

    Defined as:

    method none(--> Junction:D)

    Interprets the invocant as a list and creates a none-Junction from it.

    say so 1 == (123).none;     # OUTPUT: «False␤» 
    say so 4 == (123).none;     # OUTPUT: «True␤» 

    (Any) method list

    Defined as:

    multi method list(Any:U: -->List)
    multi method list(Any:D \SELF: -->List)

    Applies the infix , operator to the invocant and returns the resulting List:

    say 42.list.^name;           # OUTPUT: «List␤» 
    say 42.list.elems;           # OUTPUT: «1␤» 

    (Any) method push

    Defined as:

    method push(|values --> Positional:D)

    The method push is defined for undefined invocants and allows for autovivifying undefined to an empty Array, unless the undefined value implements Positional already. The argument provided will then be pushed into the newly created Array.

    my %h;
    say %h<a>;     # OUTPUT: «(Any)␤»      <-- Undefined 
    %h<a>.push(1); # .push on Any 
    say %h;        # OUTPUT: «{a => [1]}␤» <-- Note the Array 

    (Any) routine reverse

    Defined as:

    multi sub    reverse(*@list  --> Seq:D)
    multi method reverse(List:D: --> Seq:D)

    Returns a Seq with the same elements in reverse order.

    Note that reverse always refers to reversing elements of a list; to reverse the characters in a string, use flip.


    say <hello world!>.reverse;     # OUTPUT: «(world! hello)␤» 
    say reverse ^10;                # OUTPUT: «(9 8 7 6 5 4 3 2 1 0)␤» 

    (Any) method sort

    Defined as:

    multi method sort()
    multi method sort(&custom-routine-to-use)

    Sorts iterables with cmp or given code object and returns a new Seq. Optionally, takes a Callable as a positional parameter, specifying how to sort.


    say <b c a>.sort;                           # OUTPUT: «(a b c)␤» 
    say 'bca'.comb.sort.join;                   # OUTPUT: «abc␤» 
    say 'bca'.comb.sort({$^b cmp $^a}).join;    # OUTPUT: «cba␤» 
    say '231'.comb.sort(&infix:«<=>»).join;     # OUTPUT: «123␤» 

    (Any) method map

    Defined as:

    multi method map(\SELF: &block;; :$label:$item)

    map will iterate over the invocant and apply the number of positional parameters of the code object from the invocant per call. The returned values of the code object will become elements of the returned Seq.

    The :$label and :$item are useful only internally, since for loops get converted to maps. The :$label takes an existing Label to label the .map's loop with and :$item controls whether the iteration will occur over (SELF,) (if :$item is set) or SELF.

    (Any) method deepmap

    Defined as:

    method deepmap(&block --> Listis nodal

    deepmap will apply &block to each element and return a new List with the return values of &block, unless the element does the Iterable role. For those elements deepmap will descend recursively into the sublist.

    say [[1,2,3],[[4,5],6,7]].deepmap(* + 1);
    # OUTPUT: «[[2 3 4] [[5 6] 7 8]]␤» 

    (Any) method duckmap

    Defined as:

    method duckmap(&blockis rw is nodal

    duckmap will apply &block on each element and return a new list with defined return values of the block. For undefined return values, duckmap will try to descend into the element if that element implements Iterable.

    <a b c d e f g>.duckmap(-> $_ where <c d e>.any { .uc }).say;
    # OUTPUT: «(a b C D E f g)␤» 
    (('d''e'), 'f').duckmap(-> $_ where <e f>.any { .uc }).say;
    # OUTPUT: «((d E) F)␤» 

    (Any) method nodemap

    Defined as:

    method nodemap(&block --> Listis nodal

    nodemap will apply &block to each element and return a new List with the return values of &block. In contrast to deepmap it will not descend recursively into sublists if it finds elements which does the Iterable role.

    say [[1,2,3], [[4,5],6,7], 7].nodemap(*+1);
    # OUTPUT: «(4, 4, 8)␤» 
    say [[23], [4, [56]]]».nodemap(*+1)
    # OUTPUT: «((3 4) (5 3))␤» 

    The examples above would have produced the exact same results if we had used map instead of nodemap. The difference between the two lies in the fact that map flattens out slips while nodemap doesn't.

    say [[2,3], [[4,5],6,7], 7].nodemap({.elems == 1 ?? $_ !! slip});
    # OUTPUT: «(() () 7)␤» 
    say [[2,3], [[4,5],6,7], 7].map({.elems == 1 ?? $_ !! slip});
    # OUTPUT: «(7)␤» 

    (Any) method flat

    Defined as:

    method flat(--> Seq:Dis nodal

    Interprets the invocant as a list, flattens non-containerized Iterables into a flat list, and returns that list. Keep in mind Map and Hash types are Iterable and so will be flattened into lists of pairs.

    say ((12), (3), %(:42a));      # OUTPUT: «((1 2) 3 {a => 42})␤» 
    say ((12), (3), %(:42a)).flat# OUTPUT: «(1 2 3 a => 42)␤» 

    Note that Arrays containerize their elements by default, and so flat will not flatten them. You can use hyper method call to call .List method on all the inner Iterables and so de-containerize them, so that flat can flatten them:

    say [[123], [(45), 67]]      .flat# OUTPUT: «([1 2 3] [(4 5) 6 7])␤» 
    say [[123], [(45), 67]]».List.flat# OUTPUT: «(1 2 3 4 5 6 7)␤» 

    For more fine-tuned options, see deepmap, duckmap, and signature destructuring

    (Any) method eager

    Defined as:

    method eager(--> Seq:Dis nodal

    Interprets the invocant as a List, evaluates it eagerly, and returns that List.

    my  $range = 1..5;
    say $range;         # OUTPUT: «1..5␤» 
    say $range.eager;   # OUTPUT: «(1 2 3 4 5)␤» 

    (Any) method elems

    Defined as:

    method elems(--> Int:Dis nodal

    Interprets the invocant as a list, and returns the number of elements in the list.

    say 42.elems;                   # OUTPUT: «1␤» 
    say <a b c>.elems;              # OUTPUT: «3␤» 

    (Any) method end

    method end(--> Any:Dis nodal

    Interprets the invocant as a list, and returns the last index of that list.

    say 6.end;                      # OUTPUT: «0␤» 
    say <a b c>.end;                # OUTPUT: «2␤» 

    (Any) method pairup

    Defined as:

    method pairup(--> Seq:Dis nodal

    Interprets the invocant as a list, and constructs a list of pairs from it, in the same way that assignment to a Hash does. That is, it takes two consecutive elements and constructs a pair from them, unless the item in the key position already is a pair (in which case the pair is passed through, and the next list item, if any, is considered to be a key again).

    say (=> 1'b''c').pairup.perl;     # OUTPUT: «(:a(1), :b("c")).Seq␤» 

    (Any) sub exit

    Defined as:

    sub exit(Int() $status = 0)

    Exits the current process with return code $status or zero if no value has been specified. The exit value ($status), when different from zero, has to be opportunely evaluated from the process that catches it (e.g., a shell).

    exit does prevent the LEAVE phaser to be executed.

    exit should be used as last resort only to signal the parent process about an exit code different from zero, and should not be used to terminate exceptionally a method or a sub: use exceptions instead.

    It is worth noting that the only way to return an exit code different from zero from a Main function is by means of using exit.

    (Any) sub item

    Defined as:

    proto sub item(|) is pure
    multi item(\x)
    multi item(|c)
    multi item(Mu $a)

    Forces given object to be evaluated in item context and returns the value of it.

    say item([1,2,3]).perl;              # OUTPUT: «$[1, 2, 3]␤» 
    say item( %apple => 10 ) ).perl;   # OUTPUT: «${:apple(10)}␤» 
    say item("abc").perl;                # OUTPUT: «"abc"␤» 

    You can also use $ as item contextualizer.

    say $[1,2,3].perl;                   # OUTPUT: «$[1, 2, 3]␤» 
    say $("abc").perl;                   # OUTPUT: «"abc"␤» 

    (Any) method Array

    Defined as:

    method Array(--> Array:Dis nodal

    Coerce the invocant to Array.

    (Any) method List

    Defined as:

    method List(--> List:Dis nodal

    Coerce the invocant to List, using the list method.

    (Any) method Hash

    Defined as:

    proto method Hash(|) is nodal
    multi method Hash--> Hash:D)

    Coerce the invocant to Hash by invoking the method hash on it.

    (Any) method hash

    Defined as:

    proto method hash(|) is nodal
    multi method hash(Any:U: --> Hash:D)
    multi method hash(Any:D: --> Hash:D)

    Creates a new Hash, empty in the case the invocant is undefined, or coerces the invocant to an Hash in the case it is defined.

    my $d# $d is Any 
    say $d.hash# OUTPUT: {} 
    $d.append: 'a''b';
    say $d.hash# OUTPUT: {a => b} 

    (Any) method Slip

    Defined as:

    method Slip(--> Slip:Dis nodal

    Coerce the invocant to Slip.

    (Any) method Map

    Defined as:

    method Map(--> Map:Dis nodal

    Coerce the invocant to Map.

    (Any) method Bag

    Defined as:

    method Bag(--> Bag:Dis nodal

    Coerce the invocant to Bag, whereby Positionals are treated as lists of values.

    (Any) method BagHash

    Defined as:

    method BagHash(--> BagHash:Dis nodal

    Coerce the invocant to BagHash, whereby Positionals are treated as lists of values.

    (Any) method Set

    Defined as:

    method Set(--> Set:Dis nodal

    Coerce the invocant to Set, whereby Positionals are treated as lists of values.

    (Any) method SetHash

    Defined as:

    method SetHash(--> SetHash:Dis nodal

    Coerce the invocant to SetHash, whereby Positionals are treated as lists of values.

    (Any) method Mix

    Defined as:

    method Mix(--> Mix:Dis nodal

    Coerce the invocant to Mix, whereby Positionals are treated as lists of values.

    (Any) method MixHash

    Defined as:

    method MixHash(--> MixHash:Dis nodal

    Coerce the invocant to MixHash, whereby Positionals are treated as lists of values.

    (Any) method Supply

    Defined as:

    method Supply(--> Supply:Dis nodal

    Coerce the invocant first to a list by applying the invocant's .list method, and then to a Supply.

    (Any) method min

    Defined As:

    multi method min(--> Any:D)
    multi method min(&filter --> Any:D)

    Coerces to Iterable and returns the numerically smallest element.

    If a Callable positional argument is provided, each value is passed into the filter, and its return value is compared instead of the original value. The original value is still the one returned from min.

    say (1,7,3).min();       # OUTPUT:«1␤» 
    say (1,7,3).min({1/$_}); # OUTPUT:«7␤» 

    (Any) method max

    Defined As:

    multi method max(--> Any:D)
    multi method max(&filter --> Any:D)

    Coerces to Iterable and returns the numerically largest element.

    If a Callable positional argument is provided, each value is passed into the filter, and its return value is compared instead of the original value. The original value is still the one returned from max.

    say (1,7,3).max();       # OUTPUT:«7␤» 
    say (1,7,3).max({1/$_}); # OUTPUT:«1␤» 

    (Any) method minmax

    Defined As:

    multi method minmax(--> Range:D)
    multi method minmax(&filter --> Range:D)

    Returns a Range from the smallest to the largest element.

    If a Callable positional argument is provided, each value is passed into the filter, and its return value is compared instead of the original value. The original values are still used in the returned Range.

    say (1,7,3).minmax();      # OUTPUT:«1..7␤» 
    say (1,7,3).minmax({-$_}); # OUTPUT:«7..1␤» 

    (Any) method minpairs

    Defined As:

    multi method minpairs(Any:D: --> Seq:D)

    Calls .pairs and returns a Seq with all of the Pairs with minimum values, as judged by the cmp operator:

    <a b c a b c>.minpairs.perl.put# OUTPUT: «(0 => "a", 3 => "a").Seq␤» 
    %(:42a, :75b).minpairs.perl.put# OUTPUT: «(:a(42),).Seq␤» 

    (Any) method maxpairs

    Defined As:

    multi method maxpairs(Any:D: --> Seq:D)

    Calls .pairs and returns a Seq with all of the Pairs with maximum values, as judged by the cmp operator:

    <a b c a b c>.maxpairs.perl.put# OUTPUT: «(2 => "c", 5 => "c").Seq␤» 
    %(:42a, :75b).maxpairs.perl.put# OUTPUT: «(:b(75),).Seq␤» 

    (Any) method keys

    Defined As:

    multi method keys(Any:U: --> List)
    multi method keys(Any:D: --> List)

    For defined Any returns its keys after calling list on it, otherwise calls list and returns it.

    say Any.keys# OUTPUT: «()␤» 

    (Any) method flatmap

    Defined As:

    method flatmap(Any:U: &code --> Seq)

    Coerces the Any to a list by applying the .list method and uses List.flatmap on it.

    say Any.flatmap({.reverse}); # OUTPUT: «((Any))␤» 

    In the case of Any, Any.list returns a 1-item list, as is shown.

    (Any) method roll

    Defined As:

    multi method roll(--> Any)
    multi method roll($n --> Seq)

    Coerces the invocant Any to a list by applying the .list method and uses List.roll on it.

    say Any.roll;    # OUTPUT: «(Any)␤» 
    say Any.roll(5); # OUTPUT: «((Any) (Any) (Any) (Any) (Any))␤» 

    (Any) method pick

    Defined As:

    multi method pick(--> Any)
    multi method pick($n --> Seq)

    Coerces the Any to a list by applying the .list method and uses List.pick on it.

    say Any.pick;    # OUTPUT: «(Any)␤» 
    say Any.pick(5); # OUTPUT: «((Any))␤» 

    (Any) method skip

    Defined As:

    multi method skip(--> Seq)
    multi method skip($n --> Seq)

    Creates a Seq from 1-item list's iterator and uses Seq.skip on it.

    say Any.skip;      # OUTPUT: «()␤» 
    say Any.skip(5);   # OUTPUT: «()␤» 
    say Any.skip(-1);  # OUTPUT: «((Any))␤» 
    say Any.skip(*-1); # OUTPUT: «((Any))␤» 

    (Any) method prepend

    Defined As:

    multi method prepend(--> Array)
    multi method prepend(@values --> Array)

    Initializes Any variable as empty Array and calls Array.prepend on it.

    my $a;
    say $a.prepend# OUTPUT: «[]␤» 
    say $a;         # OUTPUT: «[]␤» 
    my $b;
    say $b.prepend(1,2,3); # OUTPUT: «[1 2 3]␤» 

    (Any) method unshift

    Defined As:

    multi method unshift(--> Array)
    multi method unshift(@values --> Array)

    Initializes Any variable as empty Array and calls Array.unshift on it.

    my $a;
    say $a.unshift# OUTPUT: «[]␤» 
    say $a;         # OUTPUT: «[]␤» 
    my $b;
    say $b.unshift([1,2,3]); # OUTPUT: «[[1 2 3]]␤» 

    (Any) method first

    Defined As:

    method first(Mu $matcher?:$k:$kv:$p:$end)

    Treats the Any as a 1-item list and uses List.first on it.

    say Any.first# OUTPUT: «(Any)␤» 

    (Any) method unique

    Defined As:

    method unique(:&as:&with --> Seq:D)

    Treats the Any as a 1-item list and uses List.unique on it.

    say Any.unique# OUTPUT: «((Any))␤» 

    (Any) method repeated

    Defined As:

    method repeated(:&as:&with --> Seq)

    Treats the Any as a 1-item list and uses List.repeated on it.

    say Any.repeated# OUTPUT: «()␤» 

    (Any) method squish

    Defined As:

    method squish(:&as:&with --> Seq)

    Treats the Any as a 1-item list and uses List.squish on it.

    say Any.squish# OUTPUT: «((Any))␤» 

    (Any) method permutations

    Defined As:

    method permutations(--> Seq)

    Treats the Any as a 1-item list and uses List.permutations on it.

    say Any.permutations# OUTPUT: «(((Any)))␤» 

    (Any) method categorize

    Defined As:

    method categorize(&mapper --> Hash:D)

    Treats the Any as a 1-item list and uses List.categorize on it.

    say Any.categorize({ $_ }); # OUTPUT: «{(Any) => [(Any)]}␤» 

    (Any) method classify

    Defined As:

    method classify(&mapper -->Hash:D)

    Treats the Any as a 1-item list and uses List.classify on it.

    say Any.classify({ $_ }); # OUTPUT: «{(Any) => [(Any)]}␤» 

    (Any) method produce

    (Any) method pairs

    Defined As:

    multi method pairs(Any:U:  -->List)
    multi method pairs(Any:D:  -->List)

    Returns an empty List if the invocant is undefined, otherwise converts the invocant to a List via the list method and calls List.pairs on it:

    say Any.pairs# OUTPUT: «()␤» 
    my $a;
    say $a.pairs;  # OUTPUT: «()» 
    $a =;
    say $a.pairs;  # OUTPUT: «(0 =>» 

    (Any) method antipairs

    Defined As:

    multi method antipairs(Any:U:  -->List)
    multi method antipairs(Any:D:  -->List)

    Applies the method List.antipairs to the invocant, if it is defined, after having invoked list on it. If the invocant is not defined, it returns an empty List:

    my $a;
    say $a.antipairs;      # OUTPUT: «()» 
    $a =;
    say $a.antipairs;      # OUTPUT: «( => 0)» 

    (Any) method kv

    Defined As:

    multi method kv(Any:U:  -->List)
    multi method kv(Any:D:  -->List)

    Returns an empty List if the invocant is not defined, otherwise it does invoke list on the invocant and then returns the result of List.kv on the latter:

    my $a;
    say $a.kv;      # OUTPUT: «()» 
    $a =;
    say $a.kv;      # OUTPUT: «(0» 
    say Any.kv;     # OUTPUT: «()␤» 

    (Any) method toggle

    Defined as:

    method toggle(Any:D: *@conditions where .all ~~ Callable:DBool :$off  --> Seq:D)

    Iterates over the invocant, producing a Seq, toggling whether the received values are propagated to the result on and off, depending on the results of calling Callables in @conditions:

    say ^10 .toggle: * < 4* %% 2&is-prime# OUTPUT: «(0 1 2 3 6 7)␤» 
    say ^10 .toggle: :off* > 4;              # OUTPUT: «(5 6 7 8 9)␤» 

    Imagine a switch that's either on or off (True or False), and values are produced if it's on. By default, the initial state of that switch is in "on" position, unless :$off is set to a true value, in which case the initial state will be "off".

    A Callable from the head of @conditions is taken (if any are available) and it becomes the current tester. Each value from the original sequence is tested by calling the tester Callable with that value. The state of our imaginary switch is set to the return value from the tester: if it's truthy, set switch to "on", otherwise set it to "off".

    Whenever the switch is toggled (i.e. switched from "off" to "on" or from "on" to "off"), the current tester Callable is replaced by the next Callable in @conditions, if available, which will be used to test any further values. If no more tester Callables are available, the switch will remain in its current state until the end of iteration.

    # our original sequence of elements: 
    say list ^10# OUTPUT: «(0 1 2 3 4 5 6 7 8 9)␤» 
    # toggled result: 
    say ^10 .toggle: * < 4* %% 2&is-prime# OUTPUT: «(0 1 2 3 6 7)␤» 
    # First tester Callable is `* < 4` and initial state of switch is "on". 
    # As we iterate over our original sequence: 
    # 0 => 0 < 4 === True  switch is on, value gets into result, switch is 
    #                      toggled, so we keep using the same Callable: 
    # 1 => 1 < 4 === True  same 
    # 2 => 2 < 4 === True  same 
    # 3 => 3 < 4 === True  same 
    # 4 => 4 < 4 === False switch is now off, "4" does not make it into the 
    #                      result. In addition, our switch got toggled, so 
    #                      we're switching to the next tester Callable 
    # 5 => 5 %% 2 === False  switch is still off, keep trying to find a value 
    # 6 => 6 %% 2 === True   switch is now on, take "6" into result. The switch 
    #                        toggled, so we'll use the next tester Callable 
    # 7 => is-prime(7) === True  switch is still on, take value and keep going 
    # 8 => is-prime(8) === False switch is now off, "8" does not make it into 
    #                            the result. The switch got toggled, but we 
    #                            don't have any more tester Callables, so it 
    #                            will remain off for the rest of the sequence. 

    Since the toggle of the switch's state loads the next tester Callable, setting :$off to a True value affects when first tester is discarded:

    # our original sequence of elements: 
    say <0 1 2># OUTPUT: «(0 1 2)␤» 
    # toggled result: 
    say <0 1 2>.toggle: * > 1# OUTPUT: «()␤» 
    # First tester Callable is `* > 1` and initial state of switch is "on". 
    # As we iterate over our original sequence: 
    # 0 => 0 > 1 === False  switch is off, "0" does not make it into result. 
    #                      In addition, switch got toggled, so we change the 
    #                      tester Callable, and since we don't have any more 
    #                      of them, the switch will remain "off" until the end 
    # our original sequence of elements: 
    say <0 1 2># OUTPUT: «(0 1 2)␤» 
    # toggled result: 
    say <0 1 2>.toggle: :off* > 1# OUTPUT: «(2)␤» 
    # First tester Callable is `* > 1` and initial state of switch is "off". 
    # As we iterate over our original sequence: 
    # 0 => 0 > 1 === False  switch is off, "0" does not make it into result. 
    #                       The switch did NOT get toggled this time, so we 
    #                       keep using our current tester Callable 
    # 1 => 1 > 1 === False  same 
    # 2 => 2 > 1 === True   switch is on, "2" makes it into the result 

    (Any) method tree

    Defined As:

    method tree(--> Any)

    Returns the class if it's undefined or if it's not iterable, returns the result of applying the tree method to the elements if it's Iterable.

    say Any.tree# OUTPUT: «Any␤» 

    .tree has different prototypes for Iterable elements.

    my @floors = ( 'A', ('B','C', ('E','F','G')));
    say @floors.tree(1).flat.elems# OUTPUT: «6␤» 
    say @floors.tree(2).flat.elems# OUTPUT: «2␤» 
    say @floors.tree*.join("-"), *.join(""), *.join("|" )); # OUTPUT: «A-B—C—E|F|G␤» 

    With a number, it iteratively applies tree to every element in the lower level; the first instance will apply .tree(0) to every element in the array, and likewise for the next example.

    The second prototype applies the Whatever code passed as arguments to every level in turn; the first argument will go to level 1 and so on. tree can, thus, be a great way to process complex all levels of complex, multi-level, data structures.

    (Any) method nl-out

    Defined As:

    method nl-out(--> Str)

    Returns Str with the value of "\n". See for the details.

    say OUTPUT: «␤␤» 

    (Any) method invert

    Defined As:

    method invert(--> List)

    Returns an empty List.

    say Any.invert# OUTPUT: «()␤» 

    (Any) method combinations

    Defined As:

    method combinations(--> Seq)

    Treats the Any as a 1-item list and uses List.combinations on it.

    say Any.combinations# OUTPUT: «(() ((Any)))␤» 

    (Any) method iterator

    Defined As:

    method iterator(--> Iterator)

    Coerces the Any to a list by applying the .list method and uses iterator on it.

    my $it = Any.iterator;
    say $it.pull-one# OUTPUT: «(Any)␤» 
    say $it.pull-one# OUTPUT: «IterationEnd␤» 

    (Any) method grep

    Defined As:

    method grep(Mu $matcher:$k:$kv:$p:$v --> Seq)

    Coerces the Any to a list by applying the .list method and uses List.grep on it.

    Based on $matcher value can be either ((Any)) or empty List.

    my $a;
    say $a.grep({ True }); # OUTPUT: «((Any))␤» 
    say $a.grep({ $_ });   # OUTPUT: «()␤» 

    (Any) method append

    Defined As:

    proto method append(|) is nodal {*}
    multi method append(Any:U \SELF: |values --> Array)

    In the case the instance is not a positional-thing, it instantiate it as a new Array, otherwise clone the current instance. After that, it appends the values passed as arguments to the array obtained calling Array.append on it.

    my $a;
    say $a.append# OUTPUT: «[]␤» 
    my $b;
    say $b.append((1,2,3)); # OUTPUT: «[1 2 3]␤» 

    (Any) method values

    Defined As:

    method values(--> List)

    Returns an empty List.

    (Any) method collate

    Defined As:

    method collate(--> Seq)


    (Any) method cache

    Defined As:

    method cache(--> List)

    Provides a List representation of the object itself, calling the method list on the instance.

    Routines supplied by class Mu

    IO::Special inherits from class Mu, which provides the following methods:

    (Mu) method defined

    Declared as

    multi method defined(   --> Bool:D)

    Returns False on the type object, and True otherwise.

    say Int.defined;                # OUTPUT: «False␤» 
    say 42.defined;                 # OUTPUT: «True␤» 

    Very few types (like Failure) override defined to return False even for instances:

    sub fails() { fail 'oh noe' };
    say fails().defined;            # OUTPUT: «False␤» 

    (Mu) routine defined

    Declared as

    multi sub    defined(Mu --> Bool:D)

    invokes the .defined method on the object and returns its result.

    (Mu) routine isa

    multi method isa(Mu $type     --> Bool:D)
    multi method isa(Str:D $type  --> Bool:D)

    Returns True if the invocant is an instance of class $type, a subset type or a derived class (through inheritance) of $type.

    my $i = 17;
    say $i.isa("Int");   # OUTPUT: «True␤» 
    say $i.isa(Any);     # OUTPUT: «True␤» 

    A more idiomatic way to do this is to use the smartmatch operator ~~ instead.

    my $s = "String";
    say $s ~~ Str;       # OUTPUT: «True␤» 

    (Mu) routine does

    method does(Mu $type --> Bool:D)

    Returns True if and only if the invocant conforms to type $type.

    my $d ='2016-06-03');
    say $d.does(Dateish);             # True    (Date does role Dateish) 
    say $d.does(Any);                 # True    (Date is a subclass of Any) 
    say $d.does(DateTime);            # False   (Date is not a subclass of DateTime) 

    Using the smart match operator ~~ is a more idiomatic alternative.

    my $d ='2016-06-03');
    say $d ~~ Dateish;                # OUTPUT: «True␤» 
    say $d ~~ Any;                    # OUTPUT: «True␤» 
    say $d ~~ DateTime;               # OUTPUT: «False␤» 

    (Mu) routine Bool

    multi sub    Bool(Mu --> Bool:D)
    multi method Bool(   --> Bool:D)

    Returns False on the type object, and True otherwise.

    Many built-in types override this to be False for empty collections, the empty string or numerical zeros

    say Mu.Bool;                    # OUTPUT: «False␤» 
    say;                # OUTPUT: «True␤» 
    say [123].Bool;             # OUTPUT: «True␤» 
    say [].Bool;                    # OUTPUT: «False␤» 
    say %hash => 'full' ).Bool;   # OUTPUT: «True␤» 
    say {}.Bool;                    # OUTPUT: «False␤» 
    say "".Bool;                    # OUTPUT: «False␤» 
    say 0.Bool;                     # OUTPUT: «False␤» 
    say 1.Bool;                     # OUTPUT: «True␤» 
    say "0".Bool;                   # OUTPUT: «True␤» 

    (Mu) method Capture

    Declared as:

    method Capture(Mu:D: --> Capture:D)

    Returns a Capture with named arguments corresponding to invocant's public attributes:

    class Foo {
        has $.foo = 42;
        has $.bar = 70;
        method bar { 'something else' }
    }.new.Capture.say# OUTPUT: «\(:bar("something else"), :foo(42))␤» 

    (Mu) method Str

    multi method Str(--> Str)

    Returns a string representation of the invocant, intended to be machine readable. Method Str warns on type objects, and produces the empty string.

    say Mu.Str;                     # Use of uninitialized value of type Mu in string context. 

    (Mu) routine gist

    multi sub    gist(+args --> Str)
    multi method gist(   --> Str)

    Returns a string representation of the invocant, optimized for fast recognition by humans. As such lists will be truncated at 100 elements. Use .perl to get all elements.

    The default gist method in Mu re-dispatches to the perl method for defined invocants, and returns the type name in parenthesis for type object invocants. Many built-in classes override the case of instances to something more specific that may truncate output.

    gist is the method that say calls implicitly, so say $something and say $something.gist generally produce the same output.

    say Mu.gist;        # OUTPUT: «(Mu)␤» 
    say;    # OUTPUT: «␤» 

    (Mu) routine perl

    multi method perl(--> Str)

    Returns a Perlish representation of the object (i.e., can usually be re-evaluated with EVAL to regenerate the object). The exact output of perl is implementation specific, since there are generally many ways to write a Perl expression that produces a particular value

    (Mu) method item

    method item(Mu \item:is raw

    Forces the invocant to be evaluated in item context and returns the value of it.

    say [1,2,3].item.perl;          # OUTPUT: «$[1, 2, 3]␤» 
    say %apple => 10 ).item.perl# OUTPUT: «${:apple(10)}␤» 
    say "abc".item.perl;            # OUTPUT: «"abc"␤» 

    (Mu) method self

    method self(--> Mu)

    Returns the object it is called on.

    (Mu) method clone

    method clone(*%twiddles)

    Creates a shallow clone of the invocant, including shallow cloning of private attributes. Alternative values for public attributes can be provided via named arguments with names matching the attributes' names.

    class Point2D {
        has ($.x$.y);
        multi method gist(Point2D:D:{
    my $p = => 2=> 3);
    say $p;                     # OUTPUT: «Point(2, 3)␤» 
    say $p.clone(=> -5);      # OUTPUT: «Point(2, -5)␤» 

    Note that .clone does not go the extra mile to shallow-copy @. and %. sigiled attributes and, if modified, the modifications will still be available in the original object:

    class Foo {
        has $.foo is rw = 42;
        has &.boo is rw = { say "Hi" };
        has       = <a b>;
        has %.baz       = <a b c d>;
    my $o1 =;
    with my $o2 = $o1.clone {
        .foo = 70;
        .bar = <Z Y>;
        .baz = <Z Y X W>;
        .boo = { say "Bye" };
    # Hash and Array attribute modifications in clone appear in original as well: 
    say $o1;    # OUTPUT: « => 42, bar => ["Z", "Y"], baz => {:X("W"), :Z("Y")}, …␤» 
    say $o2;    # OUTPUT: « => 70, bar => ["Z", "Y"], baz => {:X("W"), :Z("Y")}, …␤» 
    $; # OUTPUT: «Hi␤» 
    $; # OUTPUT: «Bye␤» 

    To clone those, you could implement your own .clone that clones the appropriate attributes and passes the new values to Mu.clone, for example, via nextwith. Alternatively, your own .clone could clone self first (using self.Mu::clone or callsame) and then manipulate the clone as needed, before returning it.

    class Bar {
        has = <a b>;
        has = <a b c d>;
        method clone { nextwith :foo(@!foo.clone:bar(%!bar.clone}
    my $o1 =;
    with my $o2 = $o1.clone {
        .foo = <Z Y>;
        .bar = <Z Y X W>;
    # Hash and Array attribute modifications in clone do not affect original: 
    say $o1# OUTPUT: « => ["a", "b"], bar => {:a("b"), :c("d")})␤» 
    say $o2# OUTPUT: « => ["Z", "Y"], bar => {:X("W"), :Z("Y")})␤» 

    (Mu) method new

    multi method new(*%attrinit)

    Default method for constructing (create + initialize) new objects of a class. This method expects only named arguments which are then used to initialize attributes with accessors of the same name.

    Classes may provide their own new method to override this default.

    new triggers an object construction mechanism that calls submethods named BUILD in each class of an inheritance hierarchy, if they exist. See the documentation on object construction for more information.

    (Mu) method bless

    method bless(*%attrinit --> Mu:D)

    Lower-level object construction method than new.

    Creates a new object of the same type as the invocant, uses the named arguments to initialize attributes, and returns the created object.

    You can use this method when writing custom constructors:

    class Point {
        has $.x;
        has $.y;
        multi method new($x$y{
    my $p =;

    (Though each time you write a custom constructor, remember that it makes subclassing harder).

    (Mu) method CREATE

    method CREATE(--> Mu:D)

    Allocates a new object of the same type as the invocant, without initializing any attributes.

    say Mu.CREATE.defined;  # OUTPUT: «True␤» 

    (Mu) method print

    multi method print(--> Bool:D)

    Prints value to $*OUT after stringification using .Str method without adding a newline at end.

    "abc\n".print;          # RESULT: «abc␤» 

    (Mu) method put

    multi method put(--> Bool:D)

    Prints value to $*OUT, adding a newline at end, and if necessary, stringifying non-Str object using the .Str method.

    "abc".put;              # RESULT: «abc␤» 

    (Mu) method say

    multi method say(--> Bool:D)

    Prints value to $*OUT after stringification using gist method with newline at end. To produce machine readable output use .put.

    say 42;                 # OUTPUT: «42␤» 

    (Mu) method ACCEPTS

    multi method ACCEPTS(Mu:U: $other)

    ACCEPTS is the method that smart matching with the infix ~~ operator and given/when invokes on the right-hand side (the matcher).

    The Mu:U multi performs a type check. Returns True if $other conforms to the invocant (which is always a type object or failure).

    say 42 ~~ Mu;           # OUTPUT: «True␤» 
    say 42 ~~ Int;          # OUTPUT: «True␤» 
    say 42 ~~ Str;          # OUTPUT: «False␤» 

    Note that there is no multi for defined invocants; this is to allow autothreading of junctions, which happens as a fallback mechanism when no direct candidate is available to dispatch to.

    (Mu) method WHICH

    multi method WHICH(--> ObjAt:D)

    Returns an object of type ObjAt which uniquely identifies the object. Value types override this method which makes sure that two equivalent objects return the same return value from WHICH.

    say 42.WHICH eq 42.WHICH;       # OUTPUT: «True␤» 

    (Mu) method WHERE

    method WHERE(--> Int)

    Returns an Int representing the memory address of the object.

    (Mu) method WHY

    multi method WHY(--> Pod::Block::Declarator)

    Returns the attached Pod::Block::Declarator.

    For instance:

    #| Initiate a specified spell normally 
    sub cast(Spell $s{
    #= (do not use for class 7 spells) 
    say &cast.WHY;
    # OUTPUT: «Initiate a specified spell normally␤(do not use for class 7 spells)␤» 

    See Pod declarator blocks for details about attaching Pod to variables, classes, functions, methods, etc.

    (Mu) trait is export

    multi sub trait_mod:<is>(Mu:U \type:$export!)

    Marks a type as being exported, that is, available to external users.

    my class SomeClass is export { }

    A user of a module or class automatically gets all the symbols imported that are marked as is export.

    See Exporting and Selective Importing Modules for more details.

    (Mu) method return

    method return()

    The method return will stop execution of a subroutine or method, run all relevant phasers and provide invocant as a return value to the caller. If a return type constraint is provided it will be checked unless the return value is Nil. A control exception is raised and can be caught with CONTROL.

    sub f { (1|2|3).return };
    say f(); # OUTPUT: «any(1, 2, 3)␤» 

    (Mu) method return-rw

    Same as method return except that return-rw returns a writable container to the invocant (see more details here: return-rw).

    (Mu) method emit

    method emit()

    Emits the invocant into the enclosing supply or react block.

    react { whenever supply { .emit for "foo"42.5 } {
        say "received {.^name} ($_)";
    # OUTPUT: 
    # received Str (foo) 
    # received Int (42) 
    # received Rat (0.5) 

    (Mu) method take

    method take()

    Returns the invocant in the enclosing gather block.

    sub insert($sep+@list{
        gather for @list {
            FIRST .takenext;
            take slip $sep.item
    say insert ':', <a b c>;
    # OUTPUT: «(a : b : c)␤» 

    (Mu) routine take

    sub take(\item)

    Takes the given item and passes it to the enclosing gather block.

    #| randomly select numbers for lotto 
    my $num-selected-numbers = 6;
    my $max-lotto-numbers = 49;
    gather for ^$num-selected-numbers {
        take (1 .. $max-lotto-numbers).pick(1);
    }.say;    # six random values 

    (Mu) routine take-rw

    sub take-rw(\item)

    Returns the given item to the enclosing gather block, without introducing a new container.

    my @a = 1...3;
    sub f(@list){ gather for @list { take-rw $_ } };
    for f(@a{ $_++ };
    say @a;
    # OUTPUT: «[2 3 4]␤» 

    (Mu) method so

    method so()

    Returns a Bool value representing the logical non-negation of an expression. One can use this method similarly to the English sentence: "If that is so, then do this thing". For instance,

    my @args = <-a -e -b -v>;
    my $verbose-selected = any(@argseq '-v' | '-V';
    if $ {
        say "Verbose option detected in arguments";
    } # OUTPUT: «Verbose option detected in arguments␤» 

    (Mu) method not

    method not()

    Returns a Bool value representing the logical negation of an expression. Thus it is the opposite of so.

    my @args = <-a -e -b>;
    my $verbose-selected = any(@argseq '-v' | '-V';
    if $verbose-selected.not {
        say "Verbose option not present in arguments";
    } # OUTPUT: «Verbose option not present in arguments␤» 

    Since there is also a prefix version of not, the above code reads better like so:

    my @args = <-a -e -b>;
    my $verbose-selected = any(@argseq '-v' | '-V';
    if not $verbose-selected {
        say "Verbose option not present in arguments";
    } # OUTPUT: «Verbose option not present in arguments␤»