Okay, thank you! Some assumptions, please correct me if i'm wrong:

  1. Prior 5.18.0, s/// will copy original only if one of these was set: $&, $`, $'. Interpreter will set global PL_sawampersand flag that can't be disabled later. m// is also affected by this flag.
  2. Between 5.18.0 and 5.20.0, Perl can track usage of mentioned variables separately and copy only requested part of string.
  3. Perl 5.20.0+, successful s/// match always changes string, so COW mechanism always had to copy original.

So, before 5.20 we have choice: avoid $&, $`, $' and use /p modifier to explicitly copy ${^*MATCH}. Now we can use $&, $`, $', m// don't suffer from PL_sawampersand anymore, but s/// will always copy original string, PL_sawampersand state doesn't matter, and nothing we can do with that.

In reply to Re^2: Substitution with regex and memory consumption by k-mx
in thread Substitution with regex and memory consumption by k-mx

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