diff --git a/doc/lbmref.md b/doc/lbmref.md
index 20ee0516..6d9ee724 100644
--- a/doc/lbmref.md
+++ b/doc/lbmref.md
@@ -1,112 +1,5 @@
 # LispBM language reference
 
-* [LispBM language reference](#lispbm-language-reference)
-   * [Arithmetic](#arithmetic)
-      * [-](#-)
-      * [*](#-1)
-      * [/](#-2)
-      * [mod](#mod)
-   * [Comparisons](#comparisons)
-      * [eq](#eq)
-      * [=](#-3)
-      * [>](#-4)
-      * [<](#-5)
-   * [Boolean operators](#boolean-operators)
-      * [and](#and)
-      * [or](#or)
-      * [not](#not)
-   * [Bit level operations](#bit-level-operations)
-      * [shl](#shl)
-      * [shr](#shr)
-      * [bitwise-and](#bitwise-and)
-      * [bitwise-or](#bitwise-or)
-      * [bitwise-xor](#bitwise-xor)
-      * [bitwise-not](#bitwise-not)
-   * [Low level operations](#low-level-operations)
-      * [encode-i32](#encode-i32)
-      * [encode-u32](#encode-u32)
-      * [encode-float](#encode-float)
-      * [decode](#decode)
-   * [nil and t](#nil-and-t)
-      * [nil](#nil)
-      * [t](#t)
-   * [Quotes and Quasiquotation](#quotes-and-quasiquotation)
-      * [quote](#quote)
-      * [`](#-6)
-      * [,](#-7)
-      * [,@](#-8)
-   * [Built-in operations](#built-in-operations)
-      * [eval](#eval)
-      * [eval-program](#eval-program)
-      * [type-of](#type-of)
-      * [sym-to-str](#sym-to-str)
-      * [str-to-sym](#str-to-sym)
-      * [sym-to-u](#sym-to-u)
-      * [u-to-sym](#u-to-sym)
-      * [is-fundamental](#is-fundamental)
-   * [Special forms](#special-forms)
-      * [if](#if)
-      * [lambda](#lambda)
-      * [closure](#closure)
-      * [let](#let)
-      * [define](#define)
-      * [progn](#progn)
-      * [read](#read)
-      * [read-program](#read-program)
-   * [Lists and cons cells](#lists-and-cons-cells)
-      * [car](#car)
-      * [cdr](#cdr)
-      * [cons](#cons)
-      * [.](#-9)
-      * [list](#list)
-      * [append](#append)
-      * [ix](#ix)
-      * [set-car](#set-car)
-      * [set-cdr](#set-cdr)
-   * [Arrays](#arrays)
-      * [array-read](#array-read)
-      * [array-write](#array-write)
-   * [Pattern-matching](#pattern-matching)
-      * [match](#match)
-      * [_](#_)
-      * [?](#-10)
-      * [?i28](#i28)
-      * [?u28](#u28)
-      * [?float](#float)
-   * [Concurrency](#concurrency)
-      * [spawn](#spawn)
-      * [wait](#wait)
-      * [yield](#yield)
-   * [Message-passing](#message-passing)
-      * [send](#send)
-      * [recv](#recv)
-   * [Macros](#macros)
-      * [macro](#macro)
-   * [Call With Current Continuation](#call-with-current-continuation)
-   * [Unparsable symbols](#unparsable-symbols)
-      * [no_match](#no_match)
-      * [read_error](#read_error)
-      * [type_error](#type_error)
-      * [eval_error](#eval_error)
-      * [out_of_memory](#out_of_memory)
-      * [fatal_error](#fatal_error)
-      * [out_of_stack](#out_of_stack)
-      * [division_by_zero](#division_by_zero)
-      * [variable_not_bound](#variable_not_bound)
-   * [Types](#types)
-      * [type-list](#type-list)
-      * [type-i28](#type-i28)
-      * [type-u28](#type-u28)
-      * [type-float](#type-float)
-      * [type-i32](#type-i32)
-      * [type-u32](#type-u32)
-      * [type-array](#type-array)
-      * [type-symbol](#type-symbol)
-      * [type-char](#type-char)
-      * [type-ref](#type-ref)
-      * [type-stream](#type-stream)
-
-
 ## Arithmetic
 
 ### +
@@ -734,6 +627,42 @@ Example
 ```clj
 (define apa 10)
 ```
+---
+
+### set!
+
+The `set!` form is used to change the value of some variable in an environment.
+You can use `set!` to change the value of a global definition, a local definition
+or a variable defintion (`#var`). An application of the `set!` form looks like
+`(set! var-expr val-expr)` where `var-expr` should evaluate to a symbol. The `val-expr` is evaluated before
+rebinding the variable.
+
+Examples:
+```clj
+(define a 10)
+```
+The variable `a` is now `10` in the global environment.
+```clj
+(set! 'a 20)
+```
+Now, the value of `a` will be 20. Note that `a` is quoted in the `set!` form application
+while it is not in the `define` form. This is because `define` requires the first
+argument to be a symbol while the `set!` form requires the first argument to evaluate
+into a symbol. 
+
+You can also set the value of a let bound variable.
+```clj
+(let ((a 10)) (set! 'a 20))
+```
+
+And you can change the value of a `#var`.
+
+```clj 
+(define #a 10)
+
+(set '#a 20)
+```
+`#a` is now 20. 
 
 ---