The performance drop in "ugly" compared to "ugly_cr" can be attributed to the fact that `$1` and `$2` are read-only and are re-evaluated each time they are used in a comparison. This means that every time you check `$1` or `$2`, Perl has to numify them again, which adds overhead. In contrast, "ugly_cr" assigns these values to lexicals, which are faster to access.

Perl does have to numify them again, but not for the reason given.

no warnings qw( void );

use Devel::Peek qw( Dump );

"a" =~ /(.)/s or die;

0+$1;        # Fetch and numify
Dump($1);
my $x = $1;  # Fetch
Dump($1);
[download]

...
  FLAGS = (GMG,SMG,POK,pIOK,pNOK,pPOK)
...
  FLAGS = (GMG,SMG,POK,pPOK)
...
[download]

As you can see, $1 gets numified. But every time you read from it, it gets repopulated since it's a magic variable. This wipes the previous values.

In the context of analyzing the AI's answer, it's worth noting that I missed the repeated numification in my answer. I stopped too soon.

The "any_cr" method is slower than "any" because of the additional overhead of assigning values to lexicals before performing the checks.

That can't be true since ugly_cr is way faster than ugly. The actual culprit is the overhead from the addition of capturing.

In the context of analyzing the AI's answer, it's worth noting the response is self-contradicting. According to the AI, assigning to the lexicals makes the cr version faster by only doing numification once, but it makes the cr version slower because of the addition of an assignment.