I like that idea, but it's not really safe, what with code blocks inside of regular expressions these days. 

use re 'debug';
my $x = qr/a(??{ BEGIN { die } })/;
__END__
Compiling REx "a(??{ BEGIN{ die } })"
panic: top_env

[download]

Tests with code other than die also shows the BEGIN block being executed even though the regular expression is never used.

In reply to Re^2: Assessing the complexity of regular expressions by kyle
in thread Assessing the complexity of regular expressions by kyle

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