An oldie but goodie....

#!/usr/bin/perl

#by Abigail of perlmonks.org
#Some times you have a need to fork of several children, but you want 
+to
#limit the maximum number of children that are alive at one time. Here
#are two little subroutines that might help you, mfork and afork. They
+ are very similar.
#They take three arguments,
#and differ in the first argument. For mfork, the first
#argument is a number, indicating how many children should be forked. 
+For
#afork, the first argument is an array - a child will be
#forked for each array element. The second argument indicates the maxi
+mum
#number of children that may be alive at one time. The third argument 
+is a
#code reference; this is the code that will be executed by the child. 
+One
#argument will be given to this code fragment; for mfork it will be an
+ increasing number,
#starting at one. Each next child gets the next number. For afork, the
+ array element is
#passed. Note that this code will assume no other children will be spa
+wned,
#and that $SIG {CHLD} hasn't been set to IGNORE.


mfork (10,10,\&hello);
sub hello{print "hello world\n";}

print "all done now\n";

###################################################
sub mfork ($$&) {
my ($count, $max, $code) = @_;
foreach my $c (1 .. $count) {
wait unless $c <= $max;
die "Fork failed: $!\n" unless defined (my $pid = fork);
exit $code -> ($c) unless $pid;
}
1 until -1 == wait;
}
##################################################
sub afork (\@$&) {
my ($data, $max, $code) = @_;
my $c = 0;
foreach my $data (@$data) {
wait unless ++ $c <= $max;
die "Fork failed: $!\n" unless defined (my $pid = fork);
exit $code -> ($data) unless $pid;
}
1 until -1 == wait;
}
#####################################################
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