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

my @characters = (
                  [ "h" ],
                  [ "e" ],
                  [ "l", "p", "i" ],
                  [ "l" ],
                  [ "o" ],
);

my @words = glob('{'.join("}{",map{join',',@$_}@characters).'}');

print "The possible words are:\n";
print "    $_\n" for @words;

__END__

The possible words are:
    hello
    heplo
    heilo