Cool/useful short examples of Perl?

David Precious davidp at
Mon May 30 15:36:54 BST 2011

On Monday 30 May 2011 14:27:25 'lesleyb' wrote:
> I am a little fearful people will substitute variables on the
> RHS in a CGI script without untainting first and then complain
> when the problems show up.  

Whilst I agree helping people learn about taint mode and how to untaint is 
valuable, I'm not sure it has a place in "look how simple this can be" / "how 
easy it is to do cool stuff" examples.

Taint mode can be useful, but a user trying out simple examples is unlikely to 
have enabled taint mode unless they know about it.

> [...] Even an example of how to untaint a
> 'basic' RFC822 email address?
> if ($data =~ /^([-\@\w.]+)$/) {
>   $data = $1;                     # $data now untainted
> } else {
>   die "Bad data in '$data'";      # log this somewhere
> }

I'd really not want to see people being encouraged to attempt to validate 
email addresses with a regex; that's a wheel that should not be re-invented; 
using e.g. Email::Valid to both untaint and check for validity properly would 
be a far better approach IMO.

In fact, a "how to validate an email address properly" example would probably 
be worthwhile, for instance:

    use Email::Valid;

    if (! Email::Valid->address($email_address) ) {
        print "Sorry, that email address is not valid!";


Dave P

David Precious  ("bigpresh")

   "Programming is like sex. One mistake and you have to support
   it for the rest of your life". (Michael Sinz)

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