The assignment operator = invokes either or both of the copy and int commands, depending on the types of its arguments. It leaves its left-hand arguments on the token list. It pairs multiple arguments if possible, so a b = 1 2 is equivalent to a = 1 b = 2. This was enabled in part to prepare for handling matrix dimensions as pairs of integers through an APL-style shape operator (not yet implemented).
The binary plus +, minus -, and times * operators invoke int, add, subtract, and times on their arguments as needed, and leave their result in a temporary variable on the token list.
The binary comma operator , concatenates its arguments to a new
temporary variable, using copy and concat. The unary
transpose operator 
transposes its argument to a new
temporary variable, using transpose. For example:
.% type s = \r,\r a a b b c c
Parentheses remove themselves from the token list once they have served their syntactic purpose. An unbalanced parentheses matches $, but this is an ugly habit to get into.
The save operator ` protects command arguments from removal from the token list, as described earlier.