Re^4: How to use __DATA__ efficiently, help!

[Anonyrnous Monk]

$_.=s/<--date\/\/>/$date/;

You probably meant

    $_ =~ s/<--date\/\/>/$date/;
    ...

or just (as $_ is the default anyway)

    s/<--date\/\/>/$date/;
    ...

s/// returns the number of substitutions made, so as you have it, you're appending that number to $_.