For MBS-5651 I would have loved to do something like:

l('Review the {doc|list of packaging types|target="_blank"} for help.', { doc => doc_link('Release/Packaging') })

I'm sure there are places where a |class="foo" could be useful as well, and there are probably plenty of other cases. I don't much care for how the syntax ends up being, as long as it becomes possible.

The current substitution happens in lib/MusicBrainz/Server/Translation.pm::_expand : $string =~ s/{($re)|(.*?)}/defined $args{$1} ? "<a href=\"" . $args{$1} . "\">" . (defined $args{$2} ? $args{$2} : $2) . "<\/a>" : "{$0}"/ge;

One possible way, as mentioned by Kuno in #musicbrainz-devel, is to make it accept something other than strings. This would allow us to still be able to say something similar to:

l('{url|some text}', { url => {
    href => doc_link('Some_text'),
    class => 'some-text-class',
    id => 'not-just-some-test',
    target => 'SuperFrame',
    hreflang => 'nxx',
}})

- ie., adding more power/flexibility to the developers, without increasing complexity for translators! \o/