The above does not "get modules loaded up". It runs two Perl processes each of which load a given module, try to execute the string "shell" (which will evaluate to a string, doing nothing), then exit.

Instead, the way forward is to run either perldl or pdl2 on the command line, which will load the PDL REPL. It has builtin help, and there is also the MetaCPAN page: https://metacpan.org/pod/perldl.