If you are a module, there is no need to do initializations in a BEGIN block.

Maybe you haven't found any but I certainly have. They aren't easy to run into but I still find it a valuable habit. Leaving a potentially large window for a race condition to fit into isn't my idea of a good programming technique. I suspect that future features of Perl will make this even more important to avoid.

Along those lines, I'd use base qw(Exporter) myself, though I look forward to just being able to dispatch &import and avoid the sledgehammer of inheritance. (:

I consider qr// to be new enough of a feature that if I were to use it in a module I would make it optional:

BEGIN {
    my $sub;
    if(  $] < 5.005  ) {
        $sub= 'return $_[0]';
    } else {
        $sub= 'return qr/$_[0]/';
    }
    eval "sub _qr { $sub }; 1"
      or  die $@;
}
# ...
  _split($text, map {_qr($_)} @_);
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