multiple named captures in map regex

[Cole Tierney]

Hello,

Is it possible to have more than one named capture in a map regex? When I try the following in a map:
~^/(?<a>.)(?<b>.) $a$b;

...I get [emerg] 28486#0: unknown "a$b” variable. I’ve tried "$a$b” and "${a}${b}” with no change. 

I’m running nginx/1.9.6.

Cole