I would not recommend running the whole .profile file for the cron instance. Most times there is more in your profile than the few Oracle environment variables you need. I normally get this to work using a shell script wrapper around my perl script.

So your cron would call the shell script

0 12 * * * /path/to/script.sh
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Then your shell script would set the variables and run the script

#!/bin/sh

ORACLE_HOME=/path/to/oracle
ORACLE_SID=testdb

perl /path/to/script.pl
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