We use 5.6.1 in production. This is a partial list of modules I wouldn't want to do without (in no particular order):

• Date::Calc
• Compress::Zlib
• Digest::MD5^*
• Text::CSV_XS
• GD and GD::Graph
• IO-stringy (IO::Scalar in particular)
• Storable^*
• Memoize^*
• MIME::Base64^*

-sauoq
"My two cents aren't worth a dime.";