It was almost literally JSX (except with Scala syntax instead of Javascript, of course).
An XML literal in Scala would have been:
// XML literals (to be dropped)
val mails1 = for (from, to, heading, body) <- todoList yield
<message>
<from>{from}</from><to>{to}</to>
<heading>{heading}</heading><body>{body}</body>
</message>
println(mails1)
This was replaced with "XML string interpolation", which
// XML string interpolation
val mails2 = for (from, to, heading, body) <- todoList yield xml"""
<message>
<from>${from}</from><to>${to}</to>
<heading>${heading}</heading><body>${body}</body>
</message>"""
println(mails2)
