ANSI Common Lisp   2 Syntax

2.4 Standard Macro Characters

If the reader encounters a macro character, then its associated reader macro function is invoked and may produce an object to be returned. This function may read the characters following the macro character in the stream in any syntax and return the object represented by that syntax.

Any character can be made to be a macro character. The macro characters defined initially in a conforming implementation include the following:

2.4.1  Left-Parenthesis
2.4.2  Right-Parenthesis
2.4.3  Single-Quote
2.4.4  Semicolon
2.4.5  Double-Quote
2.4.6  Backquote
2.4.7  Comma
2.4.8  Sharpsign
2.4.9  Re-Reading Abbreviated Expressions