I use palm2ical from http://hepunx.rl.ac.uk/~adye/software/palm/palm2ical/, which uses Palm::Datebook, although that doesn't do memos. However, looking at its code, plus the examples in Palm distro, gives me this code, which works for me:

use Palm::Memo;
my $pdb = Palm::PDB->new();
$pdb->Load($filename);

use Data::Dump;
dd $pdb;
[download]

Another alternative, although not Perl, is to use J-Pilot to open the files directly.