Scheme code for extracting LilyPond header properties?

[John Zaitseff]

Dear LilyPonders,

I am not a particular expert on Scheme, hence my request for help.
I am trying to write a new version of tagline that includes the
particular document maintainer's name and e-mail address.  Thus, I
have the following in my header:

    \header {
        ...
        maintainer = "John Zaitseff"
        maintainerEmail = "address@hidden"
    }

and I redefine tagline as:

    tagline = \markup {
        \teeny
        \override #'(word-space . 0)
        \line {
            % [... other information ...]
            "Document maintained by "
            \fromproperty #'header:maintainer
            "."
        }
    }

So far, so good.  What I would like to do, however, is to replace
the "\fromproperty #'header:maintainer" with something like:

    \with-url #"mailto:address@hidden";
        \fromproperty #'header:maintainer

except that I would like to extract the actual e-mail address from
header:maintainerEmail: something like:

    \with-url #(string-append "mailto:"; XXX)

It's the XXX that I'm having problems with!  How do I extract the
header:maintainerEmail property as a Scheme string?  Any help would
be much appreciated!

Yours truly,

John Zaitseff

-- 
John Zaitseff                    ,--_|\    The ZAP Group
Phone:  +61 2 9643 7737         /      \   Sydney, Australia
E-mail: address@hidden   \_,--._*   http://www.zap.org.au/
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