Actually I am not sure I know how to fix it! Have a look at this test code (it hangs). This is a minimal case that simply shows how read() will block on reads from $conn.

#!/usr/bin/perl -w

use strict;

use HTTP::Daemon;
use HTTP::Status;

my $d = HTTP::Daemon->new(
    Reuse     => 1,
    LocalPort => 80,
) or die "No daemon: $!\n";

warn "Ready to go!\n";

while (my $conn = $d->accept())
{
    serve_everything( $conn, $conn->get_request( 1 ));
}

sub serve_everything
{
    my ($conn, $req) = @_;
    my $length = $req->content_length || 0;
   local *main::STDIN = $conn;
    my $data = ''; my $buf;
    if ( $length ) {
        print "Expecting $length bytes\n";
        while( read( STDIN, $buf, 16 ) ) {
            print "Got: $buf\n";
            $data .= $buf;
        }
    }
    else {
        $data = "Nothing Posted\n";
    }

    my $HTML = qq!<pre>$data</pre>
            <hr>
            <FORM METHOD="POST" ACTION="http://localhost"  ENCTYPE="mu
+ltipart/form-data">
                <INPUT TYPE="file" NAME="upload_file1" SIZE="42">
                <INPUT TYPE="submit">
            </FORM>
            !;

    $conn->send_response(
        HTTP::Response->new(
            200, 'OK',
            HTTP::Headers->new( Content_Type => "text/html"  ) ,
            $HTML
        )
    );

    $conn->print( 'nope', $@ ) if $@;
}
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