Well, I gave you the source, so you could have easily done this yourself. Now I had to first compile a threaded Perl (as I'm on a different machine now). Anyway, I modified the program so it does it all four times: fork and wait, fork with SIGCHLD being ignored, joining threads, and detachted threads, with labels Fw, Fi, Tj and Td. Not surprisingly, there's not much difference between Fw and Fi, and between Tj and Td.

Empty childs
(Fw)     0: 0.01 user, 0.01 system, 0:00.02 elapsed
(Fi)     0: 0.01 user, 0.00 system, 0:00.01 elapsed
(Tj)     0: 0.05 user, 0.00 system, 0:00.06 elapsed
(Td)     0: 0.05 user, 0.00 system, 0:00.06 elapsed
(Fw)     5: 0.01 user, 0.00 system, 0:00.01 elapsed
(Fi)     5: 0.02 user, 0.00 system, 0:00.02 elapsed
(Tj)     5: 0.11 user, 0.02 system, 0:00.14 elapsed
(Td)     5: 0.12 user, 0.00 system, 0:00.14 elapsed
(Fw)    10: 0.01 user, 0.00 system, 0:00.03 elapsed
(Fi)    10: 0.01 user, 0.00 system, 0:00.03 elapsed
(Tj)    10: 0.20 user, 0.00 system, 0:00.24 elapsed
(Td)    10: 0.21 user, 0.00 system, 0:00.24 elapsed
(Fw)    25: 0.00 user, 0.06 system, 0:00.10 elapsed
(Fi)    25: 0.01 user, 0.01 system, 0:00.09 elapsed
(Tj)    25: 0.45 user, 0.47 system, 0:01.32 elapsed
(Td)    25: 0.42 user, 0.04 system, 0:00.58 elapsed
(Fw)    50: 0.01 user, 0.00 system, 0:00.11 elapsed
(Fi)    50: 0.01 user, 0.00 system, 0:00.16 elapsed
(Tj)    50: 0.86 user, 0.01 system, 0:01.07 elapsed
(Td)    50: 0.79 user, 0.07 system, 0:01.00 elapsed
(Fw)   100: 0.02 user, 0.00 system, 0:00.21 elapsed
(Fi)   100: 0.01 user, 0.00 system, 0:00.35 elapsed
(Tj)   100: 1.60 user, 0.12 system, 0:01.99 elapsed
(Td)   100: 1.62 user, 0.08 system, 0:01.99 elapsed
(Fw)   250: 0.01 user, 0.00 system, 0:00.50 elapsed  
(Fi)   250: 0.02 user, 0.00 system, 0:00.85 elapsed  
(Tj)   250: 4.20 user, 0.23 system, 0:05.18 elapsed
(Td)   250: 4.28 user, 0.20 system, 0:05.22 elapsed
(Fw)   500: 0.02 user, 0.00 system, 0:01.01 elapsed
(Fi)   500: 0.02 user, 0.04 system, 0:01.73 elapsed
(Tj)   500: 9.09 user, 0.56 system, 0:11.28 elapsed
(Td)   500: 9.19 user, 0.46 system, 0:11.25 elapsed  
(Fw)  1000: 0.01 user, 0.01 system, 0:02.02 elapsed  
(Fi)  1000: 0.02 user, 0.12 system, 0:03.47 elapsed
A thread exited while 48 threads were running.
(Tj)  1000: 17.54 user, 14.73 system, 3:07.04 elapsed
(Td)  1000: 22.57 user, 23.33 system, 4:38.73 elapsed

Childs writing
(Fw)     0: 0.03 user, 0.07 system, 0:01.50 elapsed
(Fi)     0: 0.02 user, 0.00 system, 0:00.01 elapsed
(Tj)     0: 0.03 user, 0.04 system, 0:00.83 elapsed
(Td)     0: 0.05 user, 0.00 system, 0:00.06 elapsed
(Fw)     5: 0.02 user, 0.00 system, 0:00.02 elapsed
(Fi)     5: 0.01 user, 0.00 system, 0:00.02 elapsed
(Tj)     5: 0.12 user, 0.02 system, 0:00.17 elapsed
(Td)     5: 0.11 user, 0.02 system, 0:00.14 elapsed
(Fw)    10: 0.01 user, 0.01 system, 0:00.03 elapsed
(Fi)    10: 0.02 user, 0.00 system, 0:00.04 elapsed
(Tj)    10: 0.19 user, 0.01 system, 0:00.23 elapsed
(Td)    10: 0.20 user, 0.01 system, 0:00.26 elapsed
(Fw)    25: 0.02 user, 0.00 system, 0:00.06 elapsed
(Fi)    25: 0.01 user, 0.00 system, 0:00.09 elapsed
(Tj)    25: 0.41 user, 0.04 system, 0:00.53 elapsed
(Td)    25: 0.45 user, 0.01 system, 0:00.53 elapsed
(Fw)    50: 0.01 user, 0.01 system, 0:00.11 elapsed
(Fi)    50: 0.02 user, 0.00 system, 0:00.18 elapsed  
(Tj)    50: 0.81 user, 0.07 system, 0:01.03 elapsed  
(Td)    50: 0.79 user, 0.07 system, 0:01.01 elapsed
(Fw)   100: 0.01 user, 0.00 system, 0:00.21 elapsed
(Fi)   100: 0.02 user, 0.00 system, 0:00.34 elapsed
(Tj)   100: 1.63 user, 0.11 system, 0:02.05 elapsed
(Td)   100: 1.63 user, 0.09 system, 0:01.99 elapsed
(Fw)   250: 0.02 user, 0.01 system, 0:00.52 elapsed  
(Fi)   250: 0.01 user, 0.00 system, 0:00.85 elapsed  
(Tj)   250: 4.22 user, 0.31 system, 0:05.29 elapsed
(Td)   250: 4.28 user, 0.20 system, 0:05.24 elapsed
(Fw)   500: 0.02 user, 0.00 system, 0:01.01 elapsed  
(Fi)   500: 0.01 user, 0.03 system, 0:01.71 elapsed  
(Tj)   500: 9.38 user, 0.51 system, 0:11.50 elapsed
(Td)   500: 9.16 user, 0.54 system, 0:11.28 elapsed
(Fw)  1000: 0.01 user, 0.00 system, 0:02.01 elapsed
(Fi)  1000: 0.02 user, 0.13 system, 0:03.49 elapsed
A thread exited while 51 threads were running.
(Tj)  1000: 17.47 user, 15.01 system, 2:34.14 elapsed
(Td)  1000: 22.57 user, 23.21 system, 5:01.54 elapsed
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Abigail