#! perl -slw
use strict;
use threads qw[ yield ];
use threads::shared;

our $MAXTIME    ||= 7200;
our $CMDS       ||= 140;
our $CONCURRENT ||= 6;

my $running :shared = 0;

my @cmds = map {
    my $time = int rand $MAXTIME;
    qq[ perl -e"sleep $time" ];
} 1 .. $CMDS;


for my $cmd ( @cmds ) {
    sleep 1 while do{ lock $running; $running >= $CONCURRENT };
    async{
        my $n = do{ lock $running; ++$running; };
        my $tid = threads->tid;
        print "$tid: starting '$cmd' ($n)";
        system $cmd;
        print "$tid: ending";
        { lock $running; --$running; }
    }->detach;
    yield;
}

sleep 1 while do{ lock $running; $running };

##</code><code>##


__END__
C:\test>t-CmdN -MAXTIME=10 -CMDS=20
1: starting ' perl -e"sleep 4" ' (1)
2: starting ' perl -e"sleep 7" ' (2)
3: starting ' perl -e"sleep 0" ' (3)
4: starting ' perl -e"sleep 3" ' (4)
3: ending
5: starting ' perl -e"sleep 0" ' (4)
6: starting ' perl -e"sleep 1" ' (5)
5: ending
7: starting ' perl -e"sleep 9" ' (5)
8: starting ' perl -e"sleep 1" ' (6)
6: ending
8: ending
9: starting ' perl -e"sleep 1" ' (5)
10: starting ' perl -e"sleep 2" ' (6)
9: ending
4: ending
11: starting ' perl -e"sleep 2" ' (5)
10: ending
12: starting ' perl -e"sleep 2" ' (5)
13: starting ' perl -e"sleep 5" ' (6)
1: ending
14: starting ' perl -e"sleep 7" ' (6)
11: ending
12: ending
15: starting ' perl -e"sleep 7" ' (5)
16: starting ' perl -e"sleep 0" ' (6)
16: ending
17: starting ' perl -e"sleep 2" ' (6)
2: ending
18: starting ' perl -e"sleep 5" ' (6)
13: ending
17: ending
19: starting ' perl -e"sleep 7" ' (5)
20: starting ' perl -e"sleep 6" ' (6)
7: ending
14: ending
15: ending
18: ending
20: ending
19: ending