There was a possibly related thread here a few months ago about character repetitions and COW but I can't locate it right now.

It would be interesting to compare with a perl that was built without the COW.
How might that be achieved on Windows ? (In fact, how is it even done on Linux ? IIRC it's fairly easily do-able on *nix but I can't find the relevant documentation.)

On Windows, I'm seeing the same thing, irrespective of whether perl-5.38.0 is built with a mingw-w64 port of gcc or with Microsoft's Visual Studio 2022. Unthreaded builds of perl fare just as poorly as the multi-thread builds.
The one thing that does make a big difference is to use a 32-bit build of perl.
For example, with a 64-bit MSVC-built perl-5.38.0: 
>perl time.pl
6.13913488388062
0.530965089797974
v5.38.0

[download]
For a 32-bit perl-5.38.0 built using the same MSVC compiler (VS2022) in 32-bit mode: 
>perl time.pl
0.0664510726928711
0.0533270835876465
v5.38.0

[download]
But even with that 32-bit build of perl, the same issue becomes evident when "1e6" is changed to "2e6": 
>perl time.pl
6.67774796485901
1.07769107818604
v5.38.0

[download]
Cheers,
Rob

In reply to Re^2: Substitution unexpectedly very slow, in Strawberry by syphilis
in thread Substitution unexpectedly very slow, in Strawberry by Anonymous Monk

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