It would help a lot if we could see some sample input - doesn't have to be the real thing, just the real structure. Meanwhile, just for the heck of it, here's a bit of cleanup for your code. I got queasy looking at all those hard 'or's and square brackets. :)

#!/usr/bin/perl -w
use strict;

my %oui;
open my $list1, "oui.txt" or die "oui.txt: $!\n";
while (<$list1>){
  if (/^(.*?) {5}\(base 16\)\t\t(.*)$/) {
     $oui{$1} = $2;
  }
}
close $list1;

while (<>){
    if (/((?:\d+\.){3}\d+).*([\w.]{14})/i){
        (my $temp = $2) =~ tr/.//d;
        print "$1 mapped to $temp for company ", $oui{substr $temp, 0,
+ 6}, "\n";
    }
}
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