#!/usr/bin/env perl

die "Usage: $0 from-file to-file\n"
  unless @ARGV == 2;

use Text::Diff;

diff shift, shift,
  { OUTPUT => \*STDOUT,
    STYLE => "OldStyle",  # or whatever pleases you
    KEYGEN => sub{ (my $line = shift) =~ s/\s*$//; return $line; },
  };