First, the operator to bind a regex match to a variable is =~ and to negate that, it's !~

Second, the operator to compare strings is eq. = is the assignment operator.

Now that that's out of the way, you could do something like: 

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

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This will first check if $contents is not empty, and if it's not, then check it against the regex, and if the regex doesn't match, then execute the body of the if statement.

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

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