The base begins with the number of components in the principal name (excluding the
realm), followed by a colon, and the pattern for building the username from the sections of
the principal name. In the pattern section $0 translates to the realm,
$1 translates to the first component and $2 to the second
component.
For example:
[1:$1@$0] translates
myusername@APACHE.ORG to
myusername@APACHE.ORG
[2:$1] translates
myusername/admin@APACHE.ORG to
myusername
[2:$1%$2] translates
myusername/admin@APACHE.ORG to
“myusername%admin
