use strict;
use warnings;

die "Can't open $ARGV[1] for write.\n"
    if !open(FH, ">>$ARGV[1]");

print FH "$$) Doing something with $ARGV[0]\n";
sleep rand 10;
print FH "$$) Finished running.\n";

##</code><code>##

use strict;
use warnings;

my $log = 'logfile.txt';

unlink $log if -e $log;
for (1..10) {
   system("perl delay.pl $_ $log &");
}

##</code><code>##

395) Doing something with 1
395) Finished running.
401) Doing something with 4
401) Finished running.
403) Doing something with 5
403) Finished running.
413) Doing something with 10
413) Finished running.
399) Doing something with 3
399) Finished running.
407) Doing something with 7
407) Finished running.
409) Doing something with 8
409) Finished running.
397) Doing something with 2
397) Finished running.
405) Doing something with 6
405) Finished running.
411) Doing something with 9
411) Finished running.