Another good place to start looking is Task::Kensho, which is

...a first cut at building a list of recommended modules....
The modules that are bundled by Task::Kensho ... are all taken from various top 100 most used perl modules lists and from discussions with various subject matter experts in the Perl Community.

The non-core module I use most often is Data::Dump, which I prefer to Data::Dumper.

Hope that helps,