For the little it's worth here, I'd take advantage of $. and $_. Minimize what you are doing millions of times; and then yes, run a handful in parallel.

open(my $fh, '<', $file) or die("Can not open file $file to read!\n");
while(<$fh>) {
    chomp;
    my ($a,$b,$c,$d,$e,$f,$g,$h,$i,$j,$k) = split("\t", $_, 11);
    # do something real
}
print "\n# of lines: $.\n";
close($fh);
[download]