use strict; use warnings; $| = 1; my $cmd = qq{$^X -le "print 'pid=', \$\$"}; for my $i (1..70) { print "$i: run $cmd ---------\n"; my $rc = system(1, $cmd); sleep(1); print "$i: done (rc=$rc).\n"; $rc < 0 and print "$i: ($!)\n"; }