I was going to write an article about using modules in Perl but Perl Maven did a better job than I ever could have. The article explains all the places Perl looks to find a given module, and how you give it alternate locations. The only thing I would add is that if you print out %INC it will list all the modules that were loaded, and from where.

use Data::Dumper;

print Dumper(\%INC);

Outputs:

$VAR1 = {
          'strict.pm' => '/usr/share/perl5/strict.pm',
          'Data/Dumper.pm' => '/usr/lib64/perl5/vendor_perl/Data/Dumper.pm',
          'warnings/register.pm' => '/usr/share/perl5/warnings/register.pm',
          'vars.pm' => '/usr/share/perl5/vars.pm',
          'overloading.pm' => '/usr/share/perl5/overloading.pm',
          'Carp.pm' => '/usr/share/perl5/vendor_perl/Carp.pm',
          'overload.pm' => '/usr/share/perl5/overload.pm',
          'constant.pm' => '/usr/share/perl5/vendor_perl/constant.pm',
          'bytes.pm' => '/usr/share/perl5/bytes.pm',
          'warnings.pm' => '/usr/share/perl5/warnings.pm',
          'XSLoader.pm' => '/usr/share/perl5/XSLoader.pm',
          'Exporter.pm' => '/usr/share/perl5/vendor_perl/Exporter.pm'
        };

Looks like Data::Dumper has quite a few dependencies.