use strict;
use Data::Dumper;

my @z = functional_unglue (
    target     => 'cowboycaddog',
    lexicon    => {
                    cowboy => undef,
                    cow    => undef,
                    boy    => undef,
                    cat    => undef,
                    dog    => undef,
                  },
    pre_images => {
        concat => sub {   
            ### this turns one long word into two
            my($x,$l) = @_;
            my @x;
            for(keys %$l){
                my $s = $_;
                if($x =~ /^\Q$s\E/){
                    push @x, [$s,substr($x,length($s))];
                }
            } @x
        },
        simple => sub {  
            ### this turns "WORD1ddWord2" into [WORD1t, dWORD2]
            my $x = shift;
            my @x;
            my %x = (
                dd => [
                    [qw(t d)],
                ],
            );
            ### it can handle arbitrary substitions, 
            ### not just dd => t|d, but XY => A|B 
            ### for any strings X,Y,A,B 
            for(keys %x){
                my $s = $_;
                if($x =~ /\Q$s\E/){
                    for my $i(0..$#{$x{$s}}){
                        my @y = (
                            $`.$x{$s}->[$i][0],
                            $x{$s}->[$i][1].$'
                        );   
                        push @x, length($y[1]) ? [@y] : [$y[0]]
                    }
                }
            } @x
        },
    }
);
@z = map{join('-',@$_)}@z;
print Dumper([@z]);