http://www.perlmonks.org?node_id=481888


in reply to Re^6: Parse::RandGen::Regexp
in thread Parse::RandGen::Regexp

You made me go back to perlre again - I knew I had looked it up when giving the original answer, but you made me second guess myself. ;-) Turns out, we're both right. Without the colon, the directive applies to the end of the current block (capturing or non-capturing parenthesis). With the colon, of course, it applies only to that non-capturing block.