Newbie: Use of "or" in XPath

I need an XPath that expresses a node set like:

/A/X|Y|Z/B

where X, Y or Z are possible children of A.
I want any B child elements of X, Y or Z.

If I try /A/X|Y|Z/B I effectively end up
with an XPath expression with 3 top level
"or" components:

/A/X or Y or Z/B

/A/*/B does work but there are elements
other than X, Y or Z that are children
of A that I want to filter out.

I can do:
/A/X/B|/A/Y/B|/A/Z/B
but that seems rather verbose and repetitive

I know I am missing something obvious.
Can anyone help me out?

kind regards,
Bern

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