Why don't you actually outsource your callbacks - as described in the Algorithm::Diff manual? The readability of your code would be significantly improved:

traverse_sequences(
    \@seq1, \@seq2,
    {   MATCH => $callback_1,
        DISCARD_A => $callback_2,
        DISCARD_B => $callback_3,
    },
    undef,     # default key-gen
    $myArgument1,
    $myArgument2,
    $myArgument3,
);

$callback_1 = sub {…};
$callback_2 = sub {…};
$callback_3 = sub {…};
[download]

Instead of:

my $str1 = shift @_;
my $str2 = shift @_;
[download]

…write: my ($str1,$str2) = @_;

The HTML thing is completely incomprehensible to me. Leave it out.