I don't understand this following code: 

defined(my $pid=fork) or die $!;
unless($pid){
exec 'date';
die $!;
}
waitpid($pid,0);

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when using fork,the fork function returns pid, which is non-zero number and true value. I don't know why I should use defined function in here. But without defined, this code just immediately die

In reply to using defined on fork by Anonymous Monk

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