Behaves like wait(2) on your system: it waits for a child
process to terminate and returns the pid of the deceased process, or
-1
 if there are no child processes.  The status is returned in
$?  and
${^CHILD_ERROR_NATIVE} .
Note that a return value of -1
 could mean that child processes are
being automatically reaped, as described in perlipc.
If you use wait in your handler for $SIG{CHLD} , it may accidentally wait for the child created by qx or system. See perlipc for details.
Portability issues: wait in perlport.