First of all print `...`; is silly. Just use system.

foreach $row ( @{$ref} ) {
     my $pid = $pm->start(@$row->[0]) and next;
     system 'alert_main.pl', '-h', $row->[0], '-p', $passId;
     print "\n";
     $pm->finish($row);
}
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Second, system ...; exit; is also silly. Just use exec.

foreach $row ( @{$ref} ) {
     my $pid = $pm->start(@$row->[0]) and next;
     exec 'alert_main.pl', '-h', $row->[0], '-p', $passId;
     $pm->finish($row);  # In case exec fails.
}
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By using exec, you only fork once per row instead of twice. Unfortunately, that's probably not enough to get rid of your problem.