and simply moves on to the next element.

And that's the bug, IMHO. If the yes-pattern is present, and the condition fails, the whole match normally fails. Why should it move on if the match fails? Compare: 

'a' =~ /^xa/ # match of x fails, doesn't move on to match a

[download]

When the no-pattern is not present, and the condition fails, it normally doesn't match: 

$ perl -wE 'say "a" =~ /^(?(?=b)xxx)a/'

$ # no match

[download]

So it doesn't show the "move on"-behavior when the yes-pattern is something else than the empty pattern.

So it's a special case. And it's not documented. So it's a bug.

Perl 6 - second systems done right

In reply to Re^2: A bug in regex with conditional subpattern? by moritz
in thread A bug in regex with conditional subpattern? by Serge314

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