#!/your/perl/here
use strict;
use warnings;
my %line = ('A' =>1,
            'B' =>1,
            'C' =>1);

# last combination to emit (based on grep filter)
my $last = 'AYW';

# build up strings for use with glob()
my @line_keys = sort keys %line;
my @tojoin = sort ('', qw (W X Y Z));
my $line_keys = join ',', @line_keys;
my $tojoin = join ',', @tojoin;

# alternation in glob uses '{string1,string2,...}'
my $glob = '{' 
           . join( '}{', 
                   $line_keys, 
                   $tojoin, 
                   $tojoin ) 
           . '}';

# globbing
@glob = glob $glob;

# only keep strings shorter than $last, 
#                or le $last
my @glob = grep length($_) < length($last) 
                || $_ le $last, 
             @glob;

# populate hash (easier ways???)
@line{@glob} = (1) x @glob;

# print results (note sort sub)
foreach my $key (sort string_length keys %line)
{
    print "$key => $line{$key}\n";
}

# sort by length, then lexicographically
sub string_length
{
    length($a) <=> length($b)
    or
    $a cmp $b
}