I wonder... A switch could be added that would tell perl that you commit to not modifying the string before utilizing $1. Then the memcopy would be unnecessary. That way you could say

$str =~ /Hulk hate (\w+)/k;
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And get the same effect. Of course the demons that would fly out of your nose if you said:

if ($str =~ /Hulk hate (\w+)/k) {
   $str='demons!';
   print $1; # could and probably would throw fatal error.
}
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Would be your problem...

BTW, if it isnt clear, this is the reason the memcpy is needed.

Alternatively, perhaps magic could be introduced to $str so that the memcpy would only happen if $str was modified while the match vars pointed at it...

A last possibility would be to not do the memcpy if the string was RO. Then you could by hand readonly the string, do the match, use $1 and then when and if you needed to modify the string undo the RO.

I guess another variant could be that the /k would result in no copy, and an understanding that accessing $1 et all would be a fatal error while that regex was the last used. However the @- @+ arrays would be populated. Its just the user would be expected to do the substring operations by hand.