Dr. J

I started writing this up earlier today, but I had to leave it to do some work. When I came back to post I saw that Abigail had already posted a solution. This solution may not be as fast as her's but it is cut and paste-able. If you want to use it feel free

I also tried to make it simple as possible.

Thanks,
Kristofer

#!/bin/perl -w

use diagnostics;
use strict;
use warnings;

############################################################
sub getAllLinesFromAFileandReturnItAsAnArray($)
{
my ($FILE) = $_[0];

  #Redundant check. This code should be unreachable just by
  #the way I defined this sub '($)'. I do manual checking
  #of each varible as an anal principle. Just my style - Kristofer
  if (!defined($FILE)) { die ("I did not receive a filename"); }

 open my $FileDescripter => $FILE or die "Could not open '$FILE'\n";
  my @ListOfStringsToReturn = <$FileDescripter>;
  close $FileDescripter;
  
  chomp @ListOfStringsToReturn;

#  my @ListOfStringsToReturn = ();
#  open (FileDescripter, "$FILE");
#  while (<FileDescripter>)
#  {
#    if (defined($_))
#    {
#      chop;
#      push @ListOfStringsToReturn, $_;
#    }
#  }
#  close(FileDescripter);


return @ListOfStringsToReturn;
}
#===========================================================

my $FirstFile = "FileOne.txt";
my $SecondFile = "FileThree.txt";
my @FileOne = getAllLinesFromAFileandReturnItAsAnArray($FirstFile);
my @FileTwo = getAllLinesFromAFileandReturnItAsAnArray($SecondFile);

for (my $i = 0; $i < @FileOne; $i++)
{
  print "Comparing Line $i in $FirstFile ... ";
  my $test = undef;
  for (my $j = 0; $j < @FileTwo; $j++)
  {
    if ($FileOne[$i] eq $FileTwo[$j])
    {
      print " matched to line $j in $SecondFile\n";
      print "  FileOne: '$FileOne[$i]'\n";
      print "  FileTwo: '$FileTwo[$j]'\n";
      #Setting j to @FileTwo will kill this loop
      $j = @FileTwo;
      $test = 0;
    }
  }
  if (!defined($test))
  {
    print " not matched. Compared to $#FileTwo entries\n";
  }
}
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Update based on Abigail's suggestion. Thanks Abigail for the lesson in Perl.