use strict;

print "Enter characters to permutate : ";
$_ = <STDIN>; s/\s+//g; split(//);

my ($last, $chars);
foreach (sort @_) {
    if ($_ ne $last) { $chars .= $_; $last = $_; }
}

for ($_ = length($chars); $_; $_--) {
    permutate($_, $chars);
}

sub permutate {
    my ($depth, $chars, $pre) = @_;
    if ($depth == 1) {
        print $pre.substr($chars,$_,1)."\n" for (0..(length($chars)-1));
    }
    else {
        for (0..(length($chars)-$depth)) {
            permutate($depth-1, substr($chars,$_+1), $pre.substr($chars,$_,1));
        }
    }
}