$text =~ s/\[([^\]]+)\]/parseLink($1)/eg;

sub parseLink {
    my $link = shift;
    my ($type, $title);
    ($type, $link, $title) = $link =~ m!(.+)://(.+)|(.+)!;
    $type ||= '';
    $title ||= $link;
    return makeLink($link, $title, $type);
}