How to regex from nginx variable with map directive

ssl_client_cert_if.conf

##
# I wanted to use same ssl client certificate CA in nginx for multple client certs
# but restrict the users outside our organisation accessing everything.
# Because I can decide what to put into the emailAddress I can force verify everything and only pass the proper users.
##

##
# This way you can restrict users only with email addresses from @koodimonni.fi
# Put this into http context in nginx configs
##

map $ssl_client_s_dn $koodimonni_user {
  default "false";
  ~emailAddress=.*@koodimonni.fi "true";
}

##
# Use the result in if
##
if ($koodimonni_user = "true") {
  proxy_pass some_super_secure_server;
}