A further syntactic construction is used to delay substitution.
When the beginning of a word starts with a curly bracket, {, it
does not do any of the above substitutions between the opening curly
bracket and its matching closing curly bracket. The word ends with the
matching closing curly bracket. This construct is used to make the
bodies of procedures in which substitutions happen when the procedure is
called, not when it is constructed. Or it is used anywhere when the
programmer does not want the normal substitutions to happen. For
example:
puts {I have $20}
will print the string I have $20 and will not try variable
substitution on the $20 part.
A word delineated by curly brackets is replaced with the characters within the brackets without performing the usual substitutions.