cpanm plays it safe by default to avoid interfering with the system Perl, but it does give hints of how to circumvent this e.g.
+% cpanm -n Attempt
! Can't write to /usr/local/share/perl5 and /usr/local/bin: Installing
+ modules to /home/arun/perl5
! To turn off this warning, you have to do one of the following:
! - run me as a root or with --sudo option (to install to /usr/local
+/share/perl5 and /usr/local/bin)
| - run me with --local-lib option e.g. cpanm --local-lib=~/perl5
! - Set PERL_CPANM_OPT="--local-lib=~/perl5" environment variable (i
+n your shell rc file)
! - Configure local::lib in your shell to set PERL_MM_OPT etc.
--> Working on Attempt
+1.tar.gz ... OK
Configuring Attempt-1.01 ... OK
Building Attempt-1.01 ... OK
Successfully installed Attempt-1.01
1 distribution installed
i.e. run it as a root or with the --sudo option, but really this is the less safe option.
Also you can avoid adding a 'use lib ...' by setting the PERL5LIB env variable (which looks already set going by what you've shown above).