In Syntax§

See primary documentation in context for Identifiers

Identifiers are grammatical building blocks that may be used to give a name to entities/objects such as constants, variables (e.g. Scalars) and routines (e.g. Subs and Methods). In a variable name, any sigil (and twigil) precedes the identifier and does not form a part thereof.

constant c = 299792458;     # identifier "c" names an Int 
my $a = 123;                # identifier "a" in the name "$a" of a Scalar 
sub hello { say "Hello!" }; # identifier "hello" names a Sub

Identifiers come in different forms: ordinary, extended, and compound identifiers.