Documentation for routine
EVAL assembled from the following types:
From Independent routines
proto sub EVAL( where Blob|Cool|Callable, Str() : = 'perl6',PseudoStash :, *)
multi sub EVAL(, Str : where ,PseudoStash :)
This routine coerces Cool
$code to Str. If
$code is a Blob, it'll be processed using the same encoding as the
$lang compiler would: for
Perl5, processes using the same rules as
This works as-is with a literal string parameter. More complex input, such as a variable or string with embedded code, is illegal by default. This can be overridden in any of several ways:
use MONKEY-SEE-NO-EVAL; # Or...use MONKEY; # shortcut that turns on all MONKEY pragmasuse Test;# any of the above allows:EVAL "say "; # OUTPUT: «10␤»
In case the
MONKEY-SEE-NO-EVAL pragma is not activated, the compiler will complain with a
EVAL is a very dangerous function!!! exception. And it is essentially right, since that will run arbitrary code with the same permissions as the program. You should take care of cleaning the code that is going to pass through EVAL if you activate the
Please note that you can interpolate to create routine names using quotation, as can be seen in this example or other ways to interpolate to create identifier names. This only works, however, for already declared functions and other objects and is thus safer to use.
Symbols in the current lexical scope are visible to code in an
my = 42;EVAL 'say $answer;'; # OUTPUT: «42␤»
However, since the set of symbols in a lexical scope is immutable after compile time, an
EVAL can never introduce symbols into the surrounding scope.
EVAL 'my $lives = 9'; say ; # error, $lives not declared
EVAL is evaluated in the current package:
say ::answer; # OUTPUT: «42␤»
And also in the current language, meaning any added syntax is available:
sub infix:<mean>(*) is assoc<list>EVAL 'say 2 mean 6 mean 4'; # OUTPUT: «4␤»
EVAL statement evaluates to the result of the last statement:
sub infix:<mean>(*) is assoc<list>say EVAL 'say 1; 2 mean 6 mean 4'; # OUTPUT: «1␤4␤»
EVAL is also a gateway for executing code in other languages:
EVAL "use v5.20; say 'Hello from perl5!'", :lang<Perl5>;
You need to have
Inline::Perl5 for this to work correctly.
It calls the subroutine form with the invocant as the first argument,
$code, passing along named args, if any.