Lexical vars in a closure

gistfile1.txt

#!/usr/bin/env perl

use warnings;
use strict;

{
	my %hsh = map { ($_ => 1) } qw( some costy hashmap here );
	sub has {
		return $hsh{$_[0]};
	}
};

print has('costy'), "\n";
print has('hash'), "\n";

Ha, well thanks for the heads up. I don't know why I totally thought subs had lexical scope. I guess my solution would have worked, albeit it was far more work than needed to be done.

Subs are "global", i.e. kept in package symbol table, which you can manipulate during runtime, e.g.

sub a_gen {
    return \&a;
}

sub a { 'outer' };

say a, a_gen->(); # says outerouter

{
    no warnings 'redefine';                                                     
    local *a = sub { 'inner' };

    say a(), a_gen->(); # says innerinner
}

say a, a_gen->(); # says outerouter