Use curly braces instead of quotes to enclose value or text in Tcl
modulefile. Within curly braces Tcl special characters like [, ] or $
are treated verbatim whereas they are evaluated within quotes.
Curly braces is Tcl recommended way to enclose verbatim content [1].
Note: if curly braces charaters are used within content, they must be
balanced. This point has been checked against current repository and no
unbalanced curly braces has been spotted.
Fixes#24243
[1] https://wiki.tcl-lang.org/page/Tcl+Minimal+Escaping+Style
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