CPAN has a lot of older code, but a lot of newer code too. Sometimes it can be hard to know what the current best-practices are, when there's so much momentum behind older more established modules.

Recommended-module lists

• Perl core
• "Extended Core" list from the Enlightened Perl Organization (background info here)
• O'Reilly's "Perl Best Practices", Appendix D
  • note: there are specific criticisms of some of its recommendations here
• Perl Advent Calendar (mirror)
• Task::BeLike::*
  • my own list
• most frequently-mentioned modules on PerlMonks [as of 2001 :| ]
• perl5i
• The Phalanx 100 (background info here)
• Perl5 wiki
• PerlNet

random others

• anything used by Perl::Critic