doubleqq:

I didn't bother trying to build sample data to test with, so I'm gonna make a few guesses. Perhaps one or more may be helpful.

First, in your inner loop, you're splitting out the @match array and *then* checking for a regular expression match to decide whether to print a row. I'd suggest checking with the regular expression first, modifying it a little to ensure that it stops at the tab, and capturing the data after the tab for printing, something like this:

   foreach my $line (@flab) {
      if ($line =~ /[^\t]*\Q$sTab[1]\E\t([^\t]+)/) {
         print RESULT "$sTab[0]\t$sTab[1]\t$2\n";
      }
   }
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Next, if you're actually checking for an exact name, rather than using a regular expression, you could just use the eq operator. Even better, if you are checking for an exact name, then you can convert @flab into a hash, and do the lookup by the name:

while (my $sLine = <LONG_LIST>) {
   chomp $sLine;
   my ($company, $name) = split /\t/, $sLine;
   if (exists $flab{$name}) {
      print RESULT "$company\t$name\t$flab{$name}{TITLE}\n";
   }
}
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If you *do* need to use a regular expression, then you may be better off creating a composite one from your @flab entries. That way you can reduce the number of regular expression searches you actually perform. If you also convert @flab into a hash, then you could do it (something) like:

my $tmp = join("|", keys %flab);
my $regex = qr/(?:$tmp)/;
while (my $sLine = <LONG_LIST>) {
   chomp $sLine;
   if ($sLine =~ $regex) {
      my ($company, $name) = split /\t/, $sLine;
      print RESULT "$company\t$name\t$flab{$name}\n";
   }
}
[download]

...roboticus

When your only tool is a hammer, all problems look like your thumb.