#!/usr/bin/perl 
use strict;
use warnings;
use Algorithm::Permute;

my $p = Algorithm::Permute->new(['a','b','c','d','e'], 3);

my @results;

while (my @res = $p->next) 
{
   push @results, [sort @res]; # use a different sort for numbers
}

my %seen;
@results = grep{!$seen{"@$_"}++ }@results; # remove duplicates!

print join ("+",@$_)."\n" for @results;