{{substituted or transcluded}} – if-then-else metatemplate that checks if a template is currently being substituted or transcluded
{{always substitute}} – For the doc of the above templates; prints a message asking for it be substituted.
{{never substitute}} – The reverse of {{always substitute}}. For the doc of templates which should not be substituted; prints a message asking for it not to be substituted.
{{may be substituted}} – For the doc of templates whose substitution is optional.
{{substitution}} – Allows free-fill description of whether the template should be substituted and under what conditions.