Usage: ON [#|+|-|^|&|@]EXEC_EXIT [-|^]<parameters> [action]
This is activated when any exec'd process exits. The parameters
are:
$0 Process number or logical name (if assigned)
$1 Signal that killed the process (or 0 if it exited normally)
$2 Exit code for process (non-zero only if $1 is 0)