Barring some special circumstances you should really be hardcoding the perl you are using. And even if there are cross-platform compatibility issues that still doesn't justify leaving it up to your PATH because you can detect the system you are on and then run a hardcoded perl from within your wrapper shell script. Or alternatively you can modify the environment from within the shell script to make sure the perl you want will be first in your path (don't forget to check for aliases too). Rolling the dice is for role-playing games, not work! :-)