0 Unfortunately, there's no easy way to distinguish between debit and credit cards from the card number.
You just have to know (for a given issuer) which ranges of numbers represent debit and credit cards.
There's a useful list here on Wikipedia:
http://en.wikipedia.org/wiki/List_of_Issuer_Identification_Numbersbut, as you'll see, trying to devise a single regular expression to make this determination would be impractical.