How do you hide panel based on certain fields from a dropdown

[UMDTERPS]

So I have been using the following SPL to hide panels based on a token from a dropdown:

<panel depends="$operating_system$">

However,  I want a few panels to only appear when "ALL" is selected, not when a individual Operating System is selected.  Is that possible using the "Depends" command?  If not, how?

Thanks!

[ITWhisperer]

The change handler for the dropdown could interrogate the value selected and set/unset a token appropriately which the panel then depends on.