How do I find out what perl modules already installed on my system?

You need to use instmodsh (interactive inventory for installed Perl modules) command to find out what modules already installed on your system.

instmodsh command provides an interactive shell type interface to query details of locally installed Perl modules. It is a little interface to ExtUtils::Installed to examine locally* installed modules, validate your packlists and even create a tarball from an installed module.

To display the list enter the following command:

[root@localhost ~]# instmodsh

Output:

Available commands are: l - List all installed modules m - Select a module q - Quit the program cmd?

type l to list all installed modules:

cmd? l Installed modules are: Config::IniFiles Perl Text::Balanced Time::HiRes cmd?