I'm trying to understand multi-threaded processes but I'm sure I've missed something. The following script identifies fake email address (yes I know no address checker is a 100%) that some of our customers give when filling in webforms (there is a big fat opt-in/opt-out question so it's nothing sleezy.) The list of addresses is long so I wanted to use threading to speed up the proccess:

#!/usr/bin/perl -w

#checks for valid email address
#usage validemail <file containing email addresses>

use warnings;
use strict;
use Email::Valid::Loose;
use Net::DNS;
use Parallel::ForkManager;
use Fcntl qw/:flock :seek/;

my $pm=new Parallel::ForkManager(20);
my $resolver=Net::DNS::Resolver->new();
my $addrfile = $ARGV[0];
my ($is_valid, $host, $x, @mx, $add, @adds, $FH);

#custom words that make emails invalid to you
my @custom = qw(
    postmaster
    webmaster
);
        

open (EMAILS, "$addrfile");

 while (<EMAILS>){
    $_ =~ s/\015//;
    chomp $_;
    push @adds, $_;
}
close (EMAILS);

#warning, I will delete existing files
$FH = "BADADDR";
open (FH, ">badmails") || die;
$FH = "GOODADDR";
open (FH, ">goodmails") || die;

foreach $add (@adds){ 
    
    $pm->start and next;

    foreach $x (@custom){
            if ($add =~ m/$x/){
                $FH = "BADADDR";
                writeaddr(); #address is bad
                $pm->finish;
            }
        }

        #if email is invalid move on
        if (!defined(Email::Valid::Loose->address($add))){
            $FH = "BADADDR";
            writeaddr(); #address is bad
            $pm->finish;
        }

        #if email is valid get domain name 
        $is_valid = Email::Valid::Loose->address($add);
        if ($is_valid =~ m/\@(.*)$/) {
            $host = $1;
        }
        $is_valid="";
        
        # perform dsn lookup to check domain
        @mx=mx($resolver, $host);

        if (@mx) {
            $FH = "GOODADDR";
            writeaddr(); #address is good
            }else{
            $FH = "BADADDR";
            writeaddr(); #address is bad
        }
       
    $pm->finish;
}

$pm->wait_all_children;

close (FH);
close (FH);

sub writeaddr{
    flock FH, LOCK_EX or die "Flock failed: $!\n";
    seek FH, SEEK_END, 0 or die "Seek failed: $!\n";
    print FH "$add\n";
    flock FH, LOCK_UN or die "unFlock failed: $!\n";
}
[download]

I receive no error messages but, nothing is written to the files. What have I missed?

Neil Watson
watson-wilson.ca

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