gistfile1.pl

# while_each_last.pl
use strict;
use warnings;

my %foo = ( foo => 'bar' );

while ( my ( $k, $v ) = each %foo ) {
    print "$k: $v\n";
    last;
}

# last でループを抜けたため、each %foo の iteration がリセットされていない

while ( my ( $k, $v ) = each %foo ) {
    print "$k: $v\n";
    last;
}

$ perl -v

This is perl 5, version 12, subversion 3 (v5.12.3) built for darwin-multi-2level
...
$ perl while_each_last.pl
foo: bar