Even better would be to use $0 as the parameter to exec.

   exec $0 unless $all_done;
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That way the script can move around on the filesystem and you won't need to hand edit it.

A warning: the above doesn't work correctly under Windows. For some reason, exec $0 spawns another copy of your script in the background. If you write a small test program like:

print "hi!\n";
sleep 2;
exec $0;
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and run it, you get the effect of:

H:\>test.pl
hi!
hi!

H:\>hi!
hi!
hi!
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What exactly it is doing, I don't know :)

mr.nick ...