CGI.pm exists in two locations.
# ls  /usr/lib/perl5/5.8.8/CGI.pm  /usr/lib/perl5/site_perl/5.8.8/CGI.pm
/usr/lib/perl5/5.8.8/CGI.pm  /usr/lib/perl5/site_perl/5.8.8/CGI.pm

Which CGI.pm are we using?
# perl -MCGI -le 'print $INC{"CGI.pm"}'
/usr/lib/perl5/site_perl/5.8.8/CGI.pm

# perl -V | tail -10
  @INC:
    /usr/lib64/perl5/site_perl/5.8.8/x86_64-linux-thread-multi
    /usr/lib/perl5/site_perl/5.8.8
    /usr/lib/perl5/site_perl
    /usr/lib64/perl5/vendor_perl/5.8.8/x86_64-linux-thread-multi
    /usr/lib/perl5/vendor_perl/5.8.8
    /usr/lib/perl5/vendor_perl
    /usr/lib64/perl5/5.8.8/x86_64-linux-thread-multi
    /usr/lib/perl5/5.8.8
    .