Forums Scripts & Popups help with invalid nick charecters please??

i want a script or if theres an identifier or regex or something
that will check if the nick typed like
input nick the input was "bla" it would return $true
or something
if it was "./@"it would return $false so it could see the charecters
that arnt aloud in nicknames

hope that was clear


please help me
thanks alot