#!/usr/bin/perl

# http://perlmonks.org/?node_id=1129709

use Algorithm::Diff qw(traverse_sequences);
use strict;
use warnings;

my (@old, @new, %dictionary);

sub addtodictionary
  {
  @old || @new and $dictionary{"@old"}{"@new"}++, @old = @new = ();
  }

while(<DATA>)
  {
  my @from = split;
  my @to = split ' ', <DATA> // 'unmatched line';

  traverse_sequences( \@from, \@to,
    {
    MATCH     => sub {addtodictionary()},
    DISCARD_A => sub {push @old, $from[shift()]},
    DISCARD_B => sub {push @new, $to[pop()]},
    } );

  addtodictionary();
  }

use YAML; print Dump \%dictionary;

__DATA__
This apple is colored red.
This apple is coloured red.
I need to buy a round trip ticket.
I need to buy a return ticket.
Jack rode the elevator to the top floor.
Jack took the lift to the top floor.

##</code><code>##

---
colored:
  coloured: 1
elevator:
  lift: 1
rode:
  took: 1
round trip:
  return: 1