print variable-name in Matlab

I have a function in Matlab that has some variables in it. I need to print out the variable_names (in case of an exception etc.). I am aware of inputname function but it works for input_arguments only.

mat = [ 1 2 ; 3 4 ] ;

% disp(['Error in var: ' ??(a)])
% desired ouput: Error in var: mat     (and NOT 1 2 ; 3 4!)

Thanks!