I don't have access to IOS-XR at the moment with which to test, but I'm not sure the same EEM libraries exist in XR that exist in IOS. However, there's nothing to keep you from adding them. At the very least, you can take the tmpsys:/lib/tcl/base64.tcl file from an IOS device, and paste that into your EEM script. You can also use the EEM user library directory on XR. Create a directory on the device to hold your library files (e.g. disk0:/lib). Copy the base64.tcl file to this directory, then configure:
event manager directory user library disk0:/lib
Then you can use the ::base64 namespace in your script.
