how to parse strings?

I have a textfield which takes hostname(eg d052) or IP address(eg 10.0.9.7)as value. i have to validate the text for hostname or ipadress.
is there any function available for parsing the text?
also i want to use regular expression to match IP address. is it possible to use regular expressions?

Did you try functions form strfunc.nsh? Is in your ${NSISDIR}\include path