Template:Tsubst tsdd
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{{subst:tsd|{{{1}}}}} gives "
start - {{{1}}} - end ".Demo for producing a substitution demo. In this case it shows the result of substituting Template:Tsd for a particular parameter value. After a change in that template it just requires pressing edit and save on the page Template:Tsubst tsdd to update the substitution demo produced by transcluding this template.
"{{tsubst tsdd|abc}}"
gives "{{subst:tsd|abc}} gives " start - abc - end "." [1]
This template Template:Tsubst tsdd uses Template:Tsubst tsd. Thus for every template like Template:Tsd two auxiliary templates are needed for producing substitution demos.