Using spam module to deter users who post phone numbers (mostly to prank their mates), I tried a couple of phone number regexps found here:

http://regexlib.com/

but now I get this error when I post a new forum thread:

warning: preg_match_all(): Unknown modifier '/' in /path/to/drupal/sites/all/modules/spam/filters/custom/custom.module on line 503

when I surround the regexp apparently because I put the regexps between '/'. But when I had not surrounded the regexp with '/', the spam module did not recognize the, so I am pretty much puzzled what to put in the spam field to do the job.

Cheers