Well, at first I wanted to say you only need to add a |(^$) to your regexp, but some experimentation has showed me that doesn't work.

Then I took a good look at you regexp. You are accepting any of a class of characters, one or more times. To accept an empty field as well, simply change the + to *: 

if ($contents != /^[\w \.\,\=\" \/<>]*$/ ){
$contentserror = "Error - message.";++$error;
}

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It's not a general answer, but in your particular case, it should work.

In reply to Re: Allow empty form fields regex by matija
in thread Allow empty form fields regex by Hissingsid

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