Using XSL variable in XQuery regular expression

Dear List,

Is it possible to use an XSL variable in a regular expression when using the
"matches" function in an XSL transformation?

Say I have
<xsl:variable name="Prefix" as="xs:string" select="'PR'"/>

Then I want to use $Prefix in my regular expression like I might use XSL
variables elsewhere:
matches(normalize-space(text()[1]), '^(optional beginning text)*$Prefix:
[a-zA-Z ]*')

$ is a special character in regular expressions.  I haven't found examples of
variables in regular expressions in my internet searching.

I'd like to match text that starts with 'PR', such as "PR1234: Some problem to
report".

I'd also like to match text that may have some other initial characters, then
the 'PR' prefix and more text, such as "optional beginning text PR9876:
Another problem".

I could put the literal 'PR' in the regular expression, but I was hoping to
factor that out for use in a few other regular expressions, and have only one
place to edit if the prefix string changed.

Thanks for suggestions, or letting me know this can't be done.

Sincerely,
Mike Cook

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