#!/usr/bin/perl -w
use strict;
use List::Permutor;

my $groups = 'LHLH';
my %count;
$count{$_}++ for split //, $groups;
my @results = $groups;
for my $key (keys %count) {
    my $perm = new List::Permutor 1 .. $count{$key};
    my @indices;
    while (my @set = $perm->next) {
        push @indices, \@set;
    }
    for my $result (@results) {
        $result =~ s/(?<=$key)/%d/g;
        $result = [map sprintf($result, @$_), @indices];
    }
    @results = map @$_, @results;
}

print join "\n", @results;