seems that there is another Perl installation on the system

it all depends how you "installed" the Strawberry. Because you used the PDL, which only comes in the portable/zip version, if you want to be using that version, you need to run its portableshell.bat to set up the environment correctly.

you can use the cmd.exe where perl command to find every instance of perl in your path; the first it lists is the first it runs across (and thus the one that will be executed). Without running portableshell.bat, I am assuming you will see that older v5.12.3 path, wherever that is, as the only result. While running portableshell.bat, I would hope you would see the Strawberry PDL v5.30.1 as the first perl.exe in the path (and maybe see the older v5.12.3 second). To install a module in the PDL edition, you would need to be inside the portableshell.bat when running cpanm Algorithm::SVM or any other perl-related commands.

You might also want to look into whether you really need the old v5.12.3 -- it depends on how/where it was installed, and whether it was another app that installed it, or just a previous standalone installation of perl. If you really do need multiple instances of perl available on Windows, and it's not caused by some other app installing a perl interpreter for its own needs (which then normally shouldn't have been put in your path), I highly recommend grabbing a copy of berrybrew, which helps manage multiple perls on the same system; the newest version that stevieb has released even allows switching between the default strawberry perls that berrybrew has already handled and "foreign" perls that you have installed elsewhere (either before or after installing berrybrew -- where "foreign" could be non-berrybrew-installed strawberries, or other perl distributions), though I haven't tried that feature yet.