#!/usr/bin/perl -w
use strict;
use IO::File;

my %hash = ();

my $f = IO::File->new("file1.txt", "r") or die "can not open file 1";
while (my $line = <$f>) {
  chomp $line;
  for my $word (split /\s*,\s*/, $line) {
     $hash{$word}++;
  }
}

my $f3 = IO::File->new("file3.txt", "w") or die "can not create file 3
+";

my $f2 = IO::File->new("file2.txt", "r") or die "can not open file 2";

while (my $line = <$f2>) {
  chomp $line;
  my @words = ();
  for my $word (split /\s*,\s*/, $line) {
    if (! exists $hash{$word}) {
      push @words, $word;
  }
  print $f3 join(",", @words), "\n";
}

undef $f;
undef $f2;
undef $f3;

# then replace file 2 with file 3...
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#!c:/perl/bin/perl.exe
use strict;
my ($file1, $file2, $file1_contents, $file2_contents,@file1_words, @fi
+le2_words, $word, $file2_new_contents);

$file1="C:/file1.txt";
$file2="C:/file2.txt";

open(FH1, "<$file1") || die "$!\n";
open(FH2, "<$file2") || die "$!\n";

$file1_contents .= $_ while(<FH1>);
$file1_contents =~ s/\s+//g;
@file1_words = split(/,/,$file1_contents);

$file2_contents .= $_ while(<FH2>);
@file2_words = split(/,/,$file2_contents);

close(FH1);
close(FH2);

foreach $word (@file1_words)
{
 @file2_words = grep {!/^\s*$word\s*$/g} @file2_words;
}

$file2_new_contents .= $_."," foreach(@file2_words);

open(FH2, ">$file2") || die "$!\n";
print FH2 $file2_new_contents;
close(FH2);
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