Let expression for multiple variables in XPath 3.0

I want to declare 2-3 variables using a function let and run a separate loop for for each variable. How can i do this?

I can use only XPath 3.0.

Thanks in advance.

I tried expressions like this, but they don't work: 1) let $x := a, $y := b return (for $var1 in $x return expr1), (for $var2 in $y return expr2)

2. return (for $var1 in $x return expr1, for $var2 in $y return expr2)

3. return for $var1 in $x return expr1, for $var2 in $y return expr2

The syntax in XPath 3.0 is

[11]    LetExpr    ::=      
          SimpleLetClause "return" ExprSingle
[12]    SimpleLetClause    ::=      
          "let" SimpleLetBinding ("," SimpleLetBinding)*
[13]    SimpleLetBinding   ::=      
          "$" VarName ":=" ExprSingle

I believe that the construct:

let $x := a, $y := b 
return (for $var1 in $x return expr1, for $var2 in $y return expr2)

should work, though I don't have an XPath 3.0 processor to try it on. It's certainly working in XPath 3.1.