yes, you are right choroba and in fact in the explanation given there is no mention of the substitution. Anyway it handles correctly the interesting part and also in this case helps a lot in spotting the wrong part.
L*
There are no rules, there are no thumbs..
Reinvent the wheel, then learn The Wheel; may be one day you reinvent one of THE WHEELS.
But it handles the incorrect part in a confusing and misleading way.
... and ... helps a lot in spotting the wrong part.
Whether it helps "a lot" or at all is open to question. But why not just fix the wrong part? Please see How do I change/delete my post?. (Of course, I'm suggesting changing your reply, not deleting it!) Perhaps also mention that YAPE::Regex::Explain only supports regex features added through Perl version 5.6.