It's not very user-friendly. You're forcing them to enter their phone number in a particular format, when you could just as easily format the number for them.

This is a pet peeve of mine. There's more than one way to punctuate phone numbers, and no standardization among web sites:

    (xxx) yyy-zzzz
    +1 xxx yyy zzzz
    xxx-yyy-zzzz
    xxxyyyzzzz
[download]

Even if your instructions are perfectly clear about the expected format, the individual using it may be used to entering it in some other form. Handling multiple formats is much more user-friendly than issuing an error message.

A simple way to handle this is to accept any old cruft they type, remove everything that isn't a digit, and make sure you got ten digits. You can then format those digits for display or whatever:

    $conphone =~ tr/0-9//dc;  # remove non-digits
    if ($conphone =~ /^(\d{3})(\d{3})(\d{4})$/) {
        $conphone = $1 . '-' . $2 . '-' . $3;
    }
    else {
        print "Bad phone! No cookie!\n";
    }
[download]