I recognize that error, but can't put my finger on it.

Put your finger on `perldoc perldiag'   :)

Can't call method ``%s'' without a package or object reference

(F) You used the syntax of a method call, but the slot filled by the object reference or package name contains an expression that returns a defined value which is neither an object reference nor a package name. Something like this will reproduce the error:

    $BADREF = 42;
    process $BADREF 1,2,3;
    $BADREF->process(1,2,3);