If you're wanting to define sub routines (or stubs) why don't you consider the path of creating it as a module instead of a config file? That'd allow you to use Exporter to do most of the work.

You can then define your callbacks as anonymous subs such as:

$printHello = sub{print "Hello world\n"};
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.. which once exporter you can of course invoke with &$printHello() - none of those nasty evals :)

Does this help or am I on the wrong track here?