s[((\w+://|www\.|WWW\.)[a-zA-Z0-9\.\@:-]+[^\"\'>< \r\t\n]*)] {
    local $_ = $1;
    my $scheme = $2;
    s/// if (my $trailing) = /([.,!?()\[\]]+$)/;
    s/&(?!\x23?\w+;)/&amp;/g;
    s/\"/&quot;/g;
    my $href = ($scheme =~ /www\./i ? "http://$_" : $_);
    qq{<a href="$href" target="_blank">$_</a>$trailing};
}eg;
[download]

is what I use.

Juerd # { site => 'juerd.nl', plp_site => 'plp.juerd.nl', do_not_use => 'spamtrap' }