Re^19: Reusing a complex regexp in multiple spots, escaping the regexp

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.

Comment on Re^19: Reusing a complex regexp in multiple spots, escaping the regexp Download Code

Replies are listed 'Best First'.
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]

Replies are listed 'Best First'.

Re^20: Reusing a complex regexp in multiple spots, escaping the regexp
by LanX (Saint) on Apr 17, 2026 at 17:07 UTC

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]