Here is a first list of the modules that are the most frequently listed as prereqs in META.yml (which is about a third of the distributions present on the CPAN). Dirty scripts which produced this are available on demand.

    87 DBI
    63 URI
    63 Kwiki
    58 Params::Validate
    56 Template
    56 DateTime
    55 LWP::UserAgent
    52 POE
    46 YAML
    41 WWW::Mechanize
    40 Class::Accessor
    34 LWP
    33 XML::LibXML
    32 Class::DBI
    32 URI::Escape
    28 Error
    28 HTML::Parser
    27 Compress::Zlib
    25 mod_perl
    25 Parse::RecDescent
    24 LWP::Simple
    24 Test::Exception
    24 Date::Parse
    24 XML::Parser
    24 Time::Piece
    23 Tk
    22 Email::Simple
    22 HTTP::Request
    22 HTML::Entities
    22 HTML::Mason
    21 File::Find::Rule
    21 Test::Pod
    20 IO::Scalar
    20 Apache::Request
    20 Digest::SHA1
    20 Clone
    19 CGI::Application
    18 IO::Zlib
    18 File::Slurp
    17 XML::Simple
    17 UNIVERSAL::require
    17 Exception::Class
    17 GD
    16 DBD::SQLite
    16 XML::RSS
    15 Class::MethodMaker
    15 Cache::Cache
    15 Pod::Simple
    15 Spiffy
    15 Class::Data::Inheritable
    15 XML::SAX
    14 Image::Size
    14 Maypole
    14 Carp::Assert
    14 HTML::TokeParser
    14 Date::Calc
    14 Test::Builder::Tester
    13 Class::Accessor::Fast
    13 Log::Log4perl
    13 Object::props
    12 HTML::Template
    12 CGI::Session
    12 DBD::mysql
    12 Inline
    12 Log::Dispatch
    12 XML::XPath
    12 HTTP::Cookies
    11 SOAP::Lite
    11 HTML::TreeBuilder
    11 Email::Address
    11 XML::LibXSLT
    11 Net::LDAP
    11 Tie::IxHash
    11 Regexp::Common
    11 Win32::OLE
    11 Term::ReadKey
    11 Archive::Tar
    10 Net::DNS
    10 IO::String
    10 HTTP::Date
    10 Module::Build
    10 CGI::Builder
    10 Apache
    10 Date::Manip
    10 load
    10 CGI::Wiki
    10 Archive::Zip
    10 Wx
    10 Apache::Cookie
    10 Image::Magick
    9 DateTime::Set
    9 Gtk2
    9 Class::Accessor::Chained
    9 Apache::Test
    9 IO::All
    9 Algorithm::Diff
    9 Mail::Sendmail
    9 Test::Pod::Coverage
    9 Email::MIME
    9 Date::Format
    9 Mail::Address
    9 Math::Symbolic
    8 Class::props
    8 Email::Valid
    8 HTML::TokeParser::Simple
    8 Exporter::Lite
    8 Apache::Session
    8 MP3::Info
    8 Locale::Maketext::Simple
    7 Object::groups
    7 File::Type
    7 GraphViz
    7 BerkeleyDB
    7 Mail::Internet
    7 Config::General
    7 URI::URL
    7 HTTP::Response
    7 HTTP::Status
    7 Module::Pluggable
    7 Text::Template
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