Allow empty form fields regex

Hissingsid has asked for the wisdom of the Perl Monks concerning the following question:

Hi,
I'm using a regex to allow input of some HTML markup into a form field but the field is still acceptable if it is empty. Here is what I'm using which seems to be validating in the way I want it to except if the field is empty then I get a false.

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

My question is: Can you please give me an example of how I can allow the field to be empty but only validate against the regex above if it has any characters in it.

I guess I could hack it by saying this first

if ($contents = ""){
$contents = "\s";
}
[download]

and then put it through the regex but that is a real mess.

Any ideas, I've done a few searches but can't find anything to help me out there.

Many thanks
Sid

20040318 Edit by Corion: Added code tags

Comment on Allow empty form fields regex Select or Download Code

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Re: Allow empty form fields regex by matija (Priest) on Mar 18, 2004 at 16:12 UTC
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; }` [download] It's not a general answer, but in your particular case, it should work.	[reply] [d/l] [select]
Re: Re: Allow empty form fields regex by Hissingsid (Sexton) on Mar 18, 2004 at 16:55 UTC
Hi, Thanks for the excellent input. I played around a bit and this is what I have got working perfectly. `if (($contents ne "") && (!($contents =~ /^[\w \.\,\=\" \/<>]+$/))){ $contentserror = "Error - message.";++$error; }` [download] For some reason this != was not helping the situation. Anyway Paladin, a big thanks I had been fiddleing for hours and now have a good solution thanks to your suggestion. Best wishes Sid Edit by castaway, added code tags	[reply] [d/l]
Re: Re: Re: Allow empty form fields regex by Hissingsid (Sexton) on Mar 18, 2004 at 17:18 UTC
Apologies guys I missed the bit about !=/!~ !~ does indeed work removing the need for some of the ()s. Many thanks Sid	[reply]
Re: Allow empty form fields regex by Paladin (Vicar) on Mar 18, 2004 at 16:08 UTC
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; }` [download] This will first check if `$contents` is not empty, and if it's not, then check it against the regex, and if the regex doesn't match, then execute the body of the if statement.	[reply] [d/l] [select]
Re: Allow empty form fields regex by tcf22 (Priest) on Mar 18, 2004 at 16:07 UTC
How about this `if ((length($contents) > 0) && ($contents !~ /^[\w \.\,\=\" \/<>]+$/)) +{ $contentserror = "Error - message.";++$error; }` [download] Also != should probably be !~. - Tom	[reply] [d/l]


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