Hi, one thing not to do is to disable strict and warnings!

After reenabling:

parent: 12158
parent 12158
    child 12159
    child 12160
    child 12161
<<<<<<<<<<<<<<<<<<<121591216012161
    child 12160
    child 12159
    child 12161
print() on closed filehandle WRITER at 1206479.pl line 29.
print() on closed filehandle WRITER at 1206479.pl line 29.
print() on closed filehandle WRITER at 1206479.pl line 29.
parent 12158
readline() on closed filehandle READER at 1206479.pl line 20.
    child 12160
Use of uninitialized value $line in chomp at 1206479.pl line 20.
print() on closed filehandle WRITER at 1206479.pl line 29.
Use of uninitialized value $line in concatenation (.) or string at 120
+6479.pl line 21.
<<<<<<<<<<<<<<<<<<<
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Fix the errors, don't silence the warnings!