Documentation leads me to believe regsub() should be supported in key field, but it is not.

Defining a key of 

mt.queue[sid.{{#NAME}.regsub("(.*)",\1)}]

results in a key of

mt.queue[sid.{ALPHA.regsub("(.*)",\1)}]

In the name field

{{#NAME}.regsub("(.*)",\1)}

results in

ALPHA

as expected.