Are you aware of the unix split utility? By default, it splits on \n, and its -C option will "put at most SIZE bytes of lines per output file".

There is also the split Perl utility, which has a -l option.

If neither of those wheels suits your purposes, you could also consider requesting to become a maintainer of the existing File::Split CPAN module. If you think there is enough overlap between your idea and that module's purpose, and the author is willing, it would solve your naming conundrum. File::Split really looks like it needs to be resuscitated. It has no passing tests on any platform/version according to the CPAN Testers reports. In fact, it only has one test, which checks next to nothing. A bug report was filed 6 years ago and has not been acknowledged. There is a chance that it has been abandoned, or maybe the author would at least appreciate it if someone revived it.

$split_rx->split or die "Can't split file: $!\n";

You probably want to create your own error variable or method instead of using $! directly: