ExtUtils::Installed provides a standard way to find out
what core and module files have been installed, and
also the versions.

#!/usr/local/bin/perl
use ExtUtils::Installed;
my $instmod = ExtUtils::Installed->new();
foreach my $module ($instmod->modules()) {
my $version = $instmod->version($module) || "???";
print "$module -- $version\n";
}
produces the following list of modules and their version


Apache::DBI -- 0.87
Apache::DBILogConfig -- 0.01
Apache::DBILogger -- 0.93
AppConfig -- 1.52
Archive::Tar -- 0.22
BerkeleyDB -- 0.06
.
.
.
.
.


Try to execute the above program to find the modules
that have been already installed and their versions.