I find this quite confusing as well.

Update: No this makes perfect sense. Thanks to dio for straightening me out.

$rx = qr{ (.) (??{ print $1 }) }x;
print "!" if "japhy" =~ $rx;
__END__
japhy

[download]

How does $1 end up being 'japhy' with this re? Interestingly, changing it to 

$rx = qr{ (.) (??{ print $1; '' }) }x;
print "!" if "japhy" =~ $rx;
__END__
j!

[download]

makes things work out properly.

---
$world=~s/war/peace/g

In reply to Re: Dynamic regex assertions, capturing groups, and parsers: joy and terror by demerphq
in thread Dynamic regex assertions, capturing groups, and parsers: joy and terror by japhy

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