Hi, @alan-kilborn and All,
I’m totally agree with you. The legal syntax is, indeed, the special conditional syntax ((?(DEFINE)...........). Just think about the word DEFINE, in upper case !
Then, an alternative syntax could be, of course, (............)(*F). Indeed, in manuals, the DEFINE part is described as a part of regex which does never match anything, by principle !
Finally, my syntax ( the third one ), although correct, should be considered as a user’s work-around !
Cheers,
guy038