The |built_in| function {.{text.prefix$}} pops the top two literals (the integer literal |pop_lit1| and a string literal, in that order). It pushes the substring of the (at most) |pop_lit1| consecutive text characters starting from the beginning of the string. This function is similar to {.{substring$}}, but this one considers an accented character (or more precisely, a ``special character''$!$, even if it's missing its matching |right_brace|) to be a single text character (rather than however many |ASCII_code| characters it actually comprises), and this function doesn't consider braces to be text characters; furthermore, this function appends any needed matching |right_brace|s. If any of the types is incorrect, it complains and pushes the null string.