sub process_request {
    my $a = shift @_;

    if (not $a =~ m!^http://.*!) {
        $a = "http://$a"
    }

    my $url = URI->new($a);
    my $host = $url->host();
    my $port = $url->port();
    my $path = $url->path();

    if ($port eq "") {
        $port = 80;
    }

    if ($path eq "") {
        $path = "/"
    }

    return ($host, $port, $path);
}
[download]

Are you sure $a will only be that? For example, 'ftp://blah.com' and 'https://somewhere.com' are valid strings for a URI which would blow up in your example since they use different schemes other than 'http'.

Perhaps a better strategy would be to let the URI module do that work for you since that's what it does best:

  my $str = shift @_;
  my $uri = URI->new($str);
  $uri->scheme('http') unless $uri->scheme;
  ...
[download]

Cheers,
Matt