Granted it took me a second to find it in your code, but the relevant question would be:
What do you mean by reference? Find out what is in the attribute? Display the contents of that attribute? actually grab a reference to the scalar contents?

So with that in mind, and the fact that you are using Tk, there must be a method within the module you are using to extract the data from your object. Probably something along the lines of

$text = $var_frame->get_attrib(textvariable);
[download]

Or something like that...

Best place to look would probably be perdoc Some::Module where Some::Module is the name of the module you are 'use'ing at the top of the script

/* And the Creator, against his better judgement, wrote man.c */