here's another way to do it: Guide to a happier unix life - screen

1. start a screen named "dirmonitor"

   bash$ screen -S dirmonitor

2. you are now inside screen; start your program

   bash$ ./dirmonitor.pl

3. press CTRL-a d to detache the screen (your program now runs in the background inside screen)

4. reattach the screen named "dirmonitor"

   bash$ screen -r dirmonitor