Node:Delaying substitution, Next:Double-quotes, Previous:Backslash substitution, Up:Syntax (Tcl)
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.