{{require subst}}: Prints an error unless substituted.
{{subst only}}: For the doc of the above templates; prints a message asking for it be substituted.
{{nosubst}}: The reverse of {{subst only}}. For the doc of templates which should not be substituted; prints a message asking for it not to be substituted.
{{substitution}}: Allows free-fill description of whether the template should be substituted and under what conditions.
