Just a thought for fun, something like the following might work, of course it is stripped to show the general idea. create an array with 9,999,999 entries. create a bit mask for each area code. place the appropriate bitmask in the array entry corresponding to the phone number, this allows you to store 8 area codes per byte of data stored. of course all edit checks, warnings etc are stripped.

#!/usr/bin/perl
open in,"987.txt" or die " could not open 987.txt as input";
# assign bit mask for this area code and pack it to binary
$a = "00000001";
$b = pack('b8',$a);
# load an array with the phone number less the area code as the subscr
+ipt
@arr;
while (<in>){
   chomp;
   $arr[$_]=$b;
}
# takes time to load about 10 seconds for all 10 million recs
print "\n\narray loaded\n";


# response for lookup is sub-second
while (true){
   print "enter phone number: ";
   $pni = <>;
   chomp $pni;
   $pna = unpack('b8',$arr[$pni]);
   if (substr($pna,7,1) eq "1" ){
     print "on file\n";
   }else{
     print "not on file\n";
   }
}
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