There's also a simple regex solution to that ;-)

#!/usr/bin/perl -w
use strict;

print 'What string would you like to twiddle? ';
chomp(my $twiddle = <STDIN>);

$twiddle =~ /^(.+?)(?{print $1,"\n";})$/; # up
chop($twiddle);
$twiddle =~ /^(.+)(?{print $1,"\n";})^/;  # down
[download]

-- Hofmator