What this means is pretty much what it says! You may well find adding the line 'use diagnostics;' to your code helpful as the diagnostics module will pull some details from the perldocs for you. For example:

use diagnostics;

0->my_method();

__DATA__
Can't call method "my_method" without a package or object reference at

    (F) You used the syntax of a method call, but the slot filled by t
+he
    object reference or package name contains an expression that retur
+ns a
    defined value which is neither an object reference nor a package n
+ame.
    Something like this will reproduce the error:
    
        $BADREF = 42;
        process $BADREF 1,2,3;
        $BADREF->process(1,2,3);
    
Uncaught exception from user code:
    Can't call method "my_method" without a package or object referenc
+e at script line 3
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So above you see an example that generates your error. Diagnostics have expanded the error message (in this case it is not the best explanation I have ever seen but....)

So the error is I called the method 'my_method' on the value 0. You can't call a method on 0 or an undefined value or in fact anthing that is not a blessed object that supports that method. The error has occurred because your Mime::Lite object is not defined for some reason. Without seeing the code you are currently working with that is all I can say.