Re^18: Reusing a complex regexp in multiple spots, escaping the regexp

Thanks for the clarification. °

Honestly, when injecting code evaluation into a variable interpolation, I'm not surprised to get inconsistent side effects.

It would be of bigger concern if it also happened with more "official" means like (?{...}) or (??{...})

Cheers Rolf
_{(addicted to the Perl Programming Language :)

see Wikisyntax for the Monastery}

°) how popular are Perl builds without thread support?

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Re^19: Reusing a complex regexp in multiple spots, escaping the regexp by dave_the_m (Monsignor) on Apr 17, 2026 at 15:29 UTC
The "code injection" was just a quick and dirty demonstration of a side-effect. Its shows that on a threaded build, the expression which defines the pattern is assembled each time, but then thrown away unused apart from the first iteration. Think for example of a tied array. The following: `for my $i (0,1) { /abc$tied_array[$i]/; }` [download] will, on threaded builds, invoke both $tied_array->FETCH(0) and $tied_array->FETCH(1), but will discard the second value. Dave.	[reply] [d/l]
Re^20: Reusing a complex regexp in multiple spots, escaping the regexp by LanX (Saint) on Apr 17, 2026 at 17:07 UTC
Thanks for the better example! Does this double execution also effect officially embedded `(?{CODE})` ? Shouldn't this be just documented with /o or (in a better world) even better emitting a warning? I'm using side effects in regexes mainly for debugging. On a tangent: My system Perl seems to be with thread support, I dunno how often Perl is even installed or used without thread support. Cheers Rolf _{(addicted to the Perl Programming Language :) see Wikisyntax for the Monastery}	[reply] [d/l]