These are the ones I (seem to) use the most:
$ find test/perl -name '*.p[lm]' -exec grep '^use ' {} \; | cut -d' '
+-f2 | perl -wle 'while(<>){ s/\s*//g; s/;//g; print}' | sort | sort
+| uniq -c | sort -rn | head -50
704 strict
606 warnings
186 Data::Dumper
175 Log::Log4perl
170 constant
135 Getopt::Long
123 Pod::Usage
106 lib
49 base
45 fields
39 vars
34 Benchmark
30 FindBin
27 DateTime
26 DBI
23 Test::More
23 File::Find
22 Term::ANSIColor
14 Time::HiRes
14 Readonly
14 Module::Install::Base
14 Exporter
13 Time::Local
13 File::Copy
13 Digest::MD5
12 XML::Writer
11 URI::Escape
11 GraphViz
10 Text::ParseWords
10 Log::Dispatch::FileRotate
10 JSON::XS
10 Config
9 Image::Imlib2
9 Date::Calc
8 POSIX
8 List::Util
8 Blog
7 Test::MockDBI
7 Storable
7 Math::BigInt
7 IPC::SysV
7 IPC::Msg
7 Carp
7 Archive::Zip
6 Test
6 File::Spec
6 Fcntl
6 Date::Manip
6 Cwd
6 Catalyst::Test
...
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No matter how great and destructive your problems may seem now, remember, you've probably only seen the tip of them. [1]