I think you have a problem in parsing the event if the regex pattern has a colon in it. Can give the hex for the colon if it is part of the pattern, but pcre also has ?: for noncapturing subpatterns. Don't know of a work around for that except not to use them (and they are worthwhile). Haven't checked but am wondering if there is a similar problem for percent sign. I am quite familiar with pcre but new to mirc scripts. Can you tell me what options the builit-in PCRE is compiled with?
