It is in a print, so a comma would be more natural than a dot. There is no need to build a single scalar when the operator takes a list. 
print config('username'), " is my username";

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Most likely the OP would want a \n in there too, but that isn't really part of the interpolation question.

In reply to Re^3: Using Subroutine Returns by doug
in thread Using Subroutine Returns by rlang

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