Construct an XML comment by computing an expression.
The following construct(s) refer to this construct:
A CompCommentConstructor constructs an XML comment by
computing the enclosed Expr. That expression is evaluated and,
after atomization, converted into a sequence of atomic values each of which is
cast into a string and concatenated with a space character between each pair of
values. It is an error if the result of the expression after atomization
contains two adjacent hyphens or if it ends with a hyphen.
This query constructs the XML comment <!--Houston, we have a
problem.-->:
let $homebase := "Houston"
return comment { string-join(($homebase, ", we have a problem."), "") }