validation of posted data.

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

hi again peeps, here is a bit of code i wrote to strip usernames of all illegal characters

 elsif ($display !~ /^\w*$/) {
    $message = $message.$errmsg ;
    $found_err = 1 ; }
[download]

currently this does not allow . in usernames. would someone please be able to re-write this to allow . thanks James