I run my ppstats like this:
perl ppstats-rc5-7.1.pl.
which explicitly calls perl to run the perl script.
As for the cron job - there are a couple ways to do this but the one way I've found that will consistently work is to su to root and then edit the /etc/crontab file to include the new job. So in mine, I have:
SHELL=/bin/bash
.
.
<other stuff>.
.
00,30 * * * * user cd /usr/ppstats-rc5-7.1.pl; perl ppstats-rc5-7.1.pl
.
.
where "00,30 * * * *" means it will run the scripts at the top and bottom of the hour (every 30 minutes), every day, week, month... and "user" = some user account that has access to go in and run the script.
The other way is to run "crontab -e -u <user>" and edit a specific file for the specified "<user>"'s cron file. If your account will do it and you're logged in as you, you can just do "crontab -e".
Again - you could try both, but I've found that the lazy way of editing /etc/crontab seems to work for me and my Red Hat 6.2.