Problem with username registration plugin

[malmazan]

PHP Code:

$this->fetch_field('username') = ucwords(strtolower($this->fetch_field('username'))); 


I made this plugin to capitalize all usernames to ensure consistency.

Though simple, i get errors ( i am very much a newbie).

errors:
Warning: preg_match(): Compilation failed: PCRE does not support \L, \l, \N, \U, or \u at offset 3 in /includes/class_dm_user.php on line 399

Parse error: syntax error, unexpected '=' in /home/..../includes/class_dm_user.php(1556) : eval()'d code on line 1

I'd appreciate some help.

Actually i believe the

Warning: preg_match(): Compilation failed: PCRE does not support \L, \l, \N, \U, or \u

error came from trying to restrict to unicode letter characters on the Admin CP Username regex