diff --git a/doc/efun/modify_command b/doc/efun/modify_command
new file mode 100644
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+++ b/doc/efun/modify_command
@@ -0,0 +1,21 @@
+SYNOPSIS
+	int|string modify_command(string cmd)
+
+DESCRIPTION
+	After set_modify_command(mob) was called for an interactive
+	object iob, all commands for that user will be passed to
+	mob->modify_command(), and the return will then be checked for
+	actions.
+
+	If the result is a string, it is the new command to execute
+	instead of the given one. Note that it is not possible to
+	make several commands from one this way!
+	If the result is a non-zero number, the given command is to
+	be ignored. In case of the closure/lfun setting this may
+	mean that the closure/lfun already executed it.
+	If the result is 0, the originally given command is to be
+	used.
+
+
+SEE ALSO
+	set_modify_command(E), hooks(C)