[exim] extract expansion item: multiple usage of key?

Hello,

specification of the
${extract{<key>}{<string1>}{<string2>}{<string3>}}
string expansion item in 11.5 is not explicit about result if
<key> is being used multiple times within <string1>.
Not having looked into the source, tests show that the value
from the first occurance of <key>... withing <string1> is
used. Can this be put down in the spec to reliably use
the fact?

Lutz

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Lutz Preßler  <Lutz.Pressler@???>    http://www.SerNet.DE/
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