memcached – How to set MEMCACHED_SERVERS environmental parameter for memcstat

I’ve installed memcached and libmemcached-tools on ubuntu 18.04.
Both of these commands work:

memcstat --servers=localhost
memcstat --servers=127.0.0.1

But in the man page for memcstat it says:

You can specify servers via the option:

–servers

or via the environment variable:

‘MEMCACHED_SERVERS, –args’

I can’t find any examples of how to set the MEMCACHED_SERVERS variable. I’ve tried:

MEMCACHED_SERVERS=127.0.0.1
MEMCACHED_SERVERS="127.0.0.1"
MEMCACHED_SERVERS="--args 127.0.0.1"
MEMCACHED_SERVERS="localhost"
MEMCACHED_SERVERS=localhost
MEMCACHED_SERVERS="--servers=localhost"

But all I get from memcstat is “No servers provided”.