I usually avoid this problem by typing 'perl' before the script name. That is:

perl foo.pl
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Then it doesn't matter what the permissions are.

I don't know of a way to automatically create .pl files with particular permissions, but you could make a cron job that does it or an alias. It would look something like:

find ~ -name \*.pl -print0 | xargs -0 chmod 755
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I don't recommend that, however. It's a little too blind for my taste.