[prettify-symbols-mode] Two consecutive matches don't work?

[Joost]

Hi,

I'm dealing with some `.xml` files that contain data which uses the sequence 
`<<!` as some sort of operator. Because it's XML, the LESS-THAN sign needs to 
be encoded as `&lt;`, yielding `&lt;&lt;!`.

So I thought this would be the ideal use case for `prettify-symbols-mode`. I 
added `("&lt;" . ?<)` to `prettify-symbols-alist` and activated the mode.

Unfortunately, only the first `&lt;` in each sequence is prettified. This seems 
to be due to the fact that the second `&lt;` is followed by the exclamation 
mark: if I insert a space in between, prettification works.

Is there any way to remedy this?

TIA

-- 
Joost Kremers
Life has its moments