I am not really sure about Windows but I assume the layer that emulates fork would also emulate this

Indeed it does. This version takes care of that, but it doesn't stop the memory leak. It might slow it a little, it is hard to tell, but there are also other problems with the fork emulation that manifest themselves.

For example, for some reason, using the DATA handle starts returning blank lines interspersed with the actual lines when forking is in use. Which doesn't happen when the fork is skipped. Just another indication that no one is using (or even properly testing) the fork emulation on windows,

He should also be checking the file opens which probably aren't doing what he thinks they are. He probably shouldn't be using bare-words file handles for this. etc. etc.

But until he explains why he feels the need to use fork here at all? There just doesn't seem any logic at all in starting a new "process" to fetch a page; pipe that content back to the parent just for it to write it to disk.

#! perl -slw
use strict;
use LWP::UserAgent;
use HTTP::Request;
use HTTP::Response;
use HTTP::Message;

my $iteration = 1;
my $some_directory = 'C:/test/junk';
#open(URLS, $some_directory.'urls.txt');
while (<DATA>) {
    my $url = $_;
    chomp $url;
    get_url($url, $iteration);
    print "($iteration) $url\n";
    #sleep 3;
    $iteration++;
}
#close URLS;

sub get_url {
    my ($url, $iteration) = @_;
    pipe(my $READER, my $WRITER);
    if (my $pid = fork) {
        close $WRITER;
        open(my $FH, '>'. "$some_directory/$iteration" ) or die $!;
        while (<$READER>) {
            print $FH $_;
        }
        close $READER;
        close $FH;
        waitpid $pid, 0;
        print "$pid returned: ", $? >> 8;
    } elsif (defined $pid) {
        close $READER;
        my $ua = LWP::UserAgent->new();
        my $request = HTTP::Request->new("GET", $url);
        my $response = $ua->request($request);
        my $content = $response->content();
        print $WRITER $content;
        close $WRITER;
        undef $request;
        undef $response;
        exit 123;
    }
}
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