$, = '|';
$DEBUG = 1;

print compare( 'Hello', 'hello' ), $/;
print compare( 'Hello', 'HELLO WORLD' ), $/;
print compare( 'The quick brown fox jumped over the lazy dogs.', 
               'The quick brown dogs jumped over the lazy fox.' ), $/;
print compare( 'The quick brown fox jumped over the lazy dogs.', 
               'The quick brown fox jumped over the lazy kangaroo.' ), $/;
print compare( 'The quick brown fox jumped over the lazy dogs.', 
               'The quick brown fox jumped, tripped and broke its neck.' ), $/;


use Algorithm::Diff qw(traverse_sequences);

sub compare {
    my ( $str1, $str2 ) = @_;
    print "\nCompare '$str1' <=> '$str2'\n" if $DEBUG;
    my $tok_str1 = tokenize($str1);
    my $tok_str2 = tokenize($str2);
    my (@match,@str1, @str2);
    traverse_sequences( $tok_str1, $tok_str2, {
        MATCH => sub { push @match, $tok_str1->[$_[0]] },
        DISCARD_A => sub { push @str1, $tok_str1->[$_[0]] },
        DISCARD_B => sub { push @str2, $tok_str2->[$_[1]] },
    });
    print "'@match' '@str1' '@str2'\n" if $DEBUG;
  return @match/(@match+@str1), @match/(@match+@str2);
}



sub tokenize {
    my ($str) = @_;
    # remove punctuation stuff
    $str =~ s/[^A-Za-z0-9 ]+//g;
    # lowercase
    $str = lc $str;
    # return array ref
  return [split ' ', $str];
}

__DATA__
Compare 'Hello' <=> 'hello'
'hello' '' ''
1|1|

Compare 'Hello' <=> 'HELLO WORLD'
'hello' '' 'world'
1|0.5|

Compare 'The quick brown fox jumped over the lazy dogs.' <=> 'The quick brown dogs jumped over the lazy fox.'
'the quick brown jumped over the lazy' 'fox dogs' 'dogs fox'
0.777777777777778|0.777777777777778|

Compare 'The quick brown fox jumped over the lazy dogs.' <=> 'The quick brown fox jumped over the lazy kangaroo.'
'the quick brown fox jumped over the lazy' 'dogs' 'kangaroo'
0.888888888888889|0.888888888888889|

Compare 'The quick brown fox jumped over the lazy dogs.' <=> 'The quick brown fox jumped, tripped and broke its neck.'
'the quick brown fox jumped' 'over the lazy dogs' 'tripped and broke its neck'
0.555555555555556|0.5|