use strict;
use Graph::Undirected;
use Graph::Directed;

my @data = qw[ xx<yy yy<zz zz>aa bb<yy yy=aa aa>cc ];

## take all equalities in the data, map each item to
## a canonical (equivalent) representative.

my $eq = Graph::Undirected->new;
$eq->add_edge( split /=/, $_ ) for grep /=/, @data;

my %canonical;
for ($eq->connected_components) {
   my $representative = $_->[0];
   for (@$_) {
      $canonical{$_} = $representative;
   }
}

sub canonical {
    exists $canonical{$_[0]} ? $canonical{$_[0]} : $_[0];
}

## take all inequalities in the data, make a dag from them
## and take the transitive closure.

my $g = Graph::Directed->new;
for (grep !/=/, @data) {
    my ($x, $y) = split /<|>/, $_;
    ($x,$y) = ($y,$x) if /</;

    $g->add_edge( canonical($x), canonical($y) );
}

die "Not a DAG!" unless $g->is_dag;
$g = $g->transitive_closure;

sub compare {
    my ($x,$y) = map canonical($_), @_;
    return  0 if $x eq $y;
    return  1 if $g->has_edge($x,$y);
    return -1 if $g->has_edge($y,$x);
    return  0;
}

my @items = qw[ aa bb cc xx yy zz ];

for my $x (@items) {
  for my $y (@items) {
     print "$x, $y: " . compare($x,$y). $/;
  }
}