Places to start:

• useful bits of info
  • the UTF8 flag, and how to check for it, and how to manually set it
  • which Perl versions implement which Unicode versions
• man pages
  • perluniintro — Perl Unicode intro
  • perlunitut — Perl Unicode tutorial
  • perlunicode — Unicode support in Perl
  • perluniprops — Unicode character properties in Perl
• core modules
  • use utf8
  • use encoding
  • bytes
  • charnames
  • Encode and related modules
  • Unicode::UCD — Unicode character database
  • Unicode::Collate — Unicode Collation Algorithm
  • Unicode::Normalize — Unicode Normalization Forms
  • enc2xs
• command-line apps
  • Unicode::Tussle — SOOOO good
  • App::Uni
• third-party modules
  • Task::Unicode