It would seem that the "eval" command isn't actually loading the cPanelUserConfig module on the host server. Only the explicit "use" statement seems to work there.

If it's not showing a warning, then it is loading it, but there's a difference: eval STRING delays the execution of the use until runtime, while normally it would run at compile time. Try adding a BEGIN { ... } block around the whole line, that'll move the execution back into compile time (see BEGIN in perlmod).