On a stylistic note, the layout that you've used:

sub main
{
  .. some code ..
  .. more code ..
}
main();
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drives me absolutely bananas.

The routine main is not, and never will be, a sub-routine. main is main. The main-line program. That's what gets run.

How about instead structuring it as

{
  .. some code ..
  .. more code ..
}
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By definition, that's implicitly main. You could even pretend it's a shell script (from whence Perl came), and do this:

.. some code ..
.. more code ..
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My personal preference is to have braces, if only to remind me that this is a procedure (even if it is really close to a shell script).