I faced a similar situation over the years as I matured with the language and discovered better ways to do things while the language improved from the early days to Perl 5. Besides applying much of the other good advice you've received here, I found that reading Damian Conway's book, "Perl Best Practices," was a great help along the way to upgrading my old code to modern Perl. (And I hope he will write a similar book for Perl 6 some day.)