Let me explain this first:

At work, a consultant gave us a set of scripts to flush out a folder of temporary files in a (perl) shopping cart and a shell script that restarts the server if it crashes.

The problem isn't that but that my boss needs to understand how everything works before he'll trust any of it. I don't really need an explaination of this as much as I just need to know if this shell command does what I think it does.

Where BAR is a file which will restart the system (just shopping cart software, not an actuall reboot), I believe that this tells the shell that BAR is the only file that can run in 'unsafe' mode: thus being able to interrupt the normal I/O chain to restart the perl server, yet the rest of perl runs in 'safe' mode.

I'm not an expert, but if anyone can let me know if I'm correct, please let me know so we can get our site working again. Thanks.

You'd rather ask this to the programming forum as this is not really Solaris specific
All I can tell is that this command is passing a variable to the BAR command through the environment.
The rest is perl, which I'm not an expert in, and never will