I have one word you should remember if you want to write maintainable perl code.

Tests

Lots of them. Ones that can be automatically run. Ones that take advantage of Test::More and integrate with the normal module build/distribute mechanisms.

Once you have a good test suite you immediately get lots of help with maintainability:

• Have I broken anything? Run the test suite.
• How is this piece of code supposed to be used? Look at the test suite.
• Does everything still work after I upgrade module Foo? Run the test suite.
• Does it still work on that box running perl 5.0? Run the test suite.
• ...etc...

Tests are good. Write more tests and future developers will sing your praises.