Can I program Tasker-like programs to do stuff if specific WiFi network is in range? I'd like to try out Tasker, Llama or some such automated program.

However, I do NOT want to program events based on GPS or other location information (for a variety of reasons not germane to this question).

Is there a way to trigger tasks in Tasker or some equivalent program based on the fact that a WiFi network with a specific SSID (or other signature) is in range or goes out of range?

To clarify: one of the main tasks is to turn on/off my WiFi when I float in/out of the range of known networks. Therefore, merely being in range should be the trigger, NOT connected to the network.
In Tasker create a new State based context and choose Net as
state category.
 

Then choose Wifi Near as net action:
 


This will bring a screen where you can input data about the WiFi access point you are interested in. If you are near the desired WiFi access point then you could just press the scan button (the button with lens symbol at left end of the text SSID).

This scans the near by access points and lists its details. Simply select the one which you are interested in.  Now you are good to go to add an entry task and exit task to whatever you want.