in reply to poll ideas quest 2011
Though not strictly a module, more a pragma, use strict; is still by far my favorite :).
DBI (you should make all modules link to CPAN), is mostly hidden behind some other module in our development environment. So next to strict, in order of favorite-ness, that would be warnings, Getopt::Long, Data::Peek, Text::CSV_XS, DBI, DBD::Pg, DBD::SQLite, DBD::Unify, DBD::CSV, autodie (likely to rise in this order), JSON, WWW::Mechanize, HTML::TreeBuilder, XML::Simple to name just a few.
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5.003 (Camel Book 2nd Edition)
5.6 (Camel Book 3rd Edition)
5.8 (stable version for >5 years)
5.10 (many new features now in common use)
5.16 (Camel Book 4th Edition)
5.18 (hash overhaul)
5.26 (no "." in @INC)
5.36 (subroutine signatures)
Dynamic (no standard; code dictates VERSION)
Other (discuss in comments)
Results (31 votes). Check out past polls.