You need the module to be imported before the rest of the file is parsed, so you need to use a BEGIN block. (A normal use, without the eval, implicitly creates its own BEGIN block.) 
BEGIN {
  $desired_module = ...
  eval "use $desired_module";
}
...
function_from_desired_module;   # should be OK now.

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In reply to Re: eval use, exported functions, barewords by simonm
in thread eval use, exported functions, barewords by Anonymous Monk

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