test.pl

use strict;
use warnings;

my %stuff = ( 
    a => 1,
    b => 2,
    c => 3,
);

while (my ($k, $v) = each %stuff) {
    print "Key: $k, value: $v\n";
    do_stuff();
}

sub do_stuff {
    print "Keys: " . join(', ' => keys %stuff) . "\n";
}