Substitute differs from substitute
in so far as its first argument can be a variable that
contains an object of mode "language". In that case,
substitutions take place inside this object.
Usage
Substitute(lang,with)
Value
An object of storage mode "language" or "symbol".
Arguments
lang
any object, unevaluated expression, or
unevaluated language construct, such as a sequence
of calls inside braces
with
a named list, environment, data frame or data set.
Details
The function body is just
do.call("substitute",list(lang,with)).