#!/usr/bin/perl -wl

print map "[$_]", "bogus firstblahj?keblahthird bogus" =~ /
    (?| (*F)
		| first ( (blah) .*? \2 ) third (?{ $L = $1 }) (*THEN) (*F)
		#       1 2    2        1
		| (??{ defined $L ? "" : "(*F)" })
		  (first) (??{ print "mid-match:[$L]" ; quotemeta $L }) (third)
		# 1     1                                               2     2
		)
    /x;