Close all figures except specific (previously tagged) ones

This is a variant of "close all figures except those listed" (http://uk.mathworks.com/matlabcentral/fileexchange/24420-close-all-figures-except-those-listed).
In this version you first tag the figures that you want to keep. Then, at anytime during the code, you can close all the figures but the tagged one by calling "cluk" (close all unkept).
For example, let's say you have 6 figure, 1 2 3 10 13 50.
with keepFig([3 10]) you will tag figure 3 and 10. This will not change the appearance of the figures in anyway.
At anypoint in the code, you can call cluk, which will close all the figures except figure 3 and 10.
You can untag all the figures by calling keepFig(-Inf). You can untag a specific figure by calling the negative of that figure's number (for example, if you want to untag figure 3, call keepFig(-3)).
You can tag all the figures by calling keepFig(Inf).
Enjoy!