From what I can tell, Crypt::OpenPGP does not support streaming. Even if you pass it a file name, the very first thing it does is slurp the contents into a variable.

What about piping your data to a command-line version of PGP? I.e., something like:

open(PGP, "|gpg -output file -encrypt -recipient ...");
while (<FH>) { print PGP }
close(PGP);
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