<issue_start><issue_comment>Title: RegExp raises exception under MacOs (PCRE error -5)
username_0: Hi all,

I'm facing a strange issue using one specific Poco::RegularExpression under MacOs, which is systematically raising an exception (PCRE error -5).  It's working perfectly under my Windows config. (I'm using old poco 1.6.1, XCode 3.2.6/llvm 4.2, OsX 10.6 SDK):

Poco::RegularExpression RE("([CMYK])\\s*=\\s*([0-9]+\\.?[0-9]*)") 
(supposed to recognize CMYK color definitions, for example C=0,M=0,Y=0,K=0)

Exception is raised at match method call.

If you've have some ideas, remarks, suggestions :)

Thanks in advance<issue_closed>