# iterator
sort { $a cmp $b } @array;
# callback
sub myFunc { $a cmp $b }
sort myFunc @array;

##</code><code>##

   package MyDiff;
   @MyDiff::ISA = 'Algorithm::Diff';
   sub keyGen { ... }
   sub compare { ... }
   sub match { ... }
   sub skip_a { ... }

   package main;
   my $diff = MyDiff->new();
   $diff->traverse_sequences(\@a1, \@a2);