[2.1] Identifiers may contain special characters if delimited with | ... |.
[2.3] The brackets [ ... ] are provided as an alternative syntax for ( ... ). A number of reader extensions is provided. See 5.3.
[4] Numerous non-standard macros are provided. See 5.4 for more information.
[4.2.3] (begin) is allowed in non-toplevel contexts and evaluates to an unspecified value.
[4.2.5] Delayed expressions may return multiple values.
[5.2.1] A define occurring anywhere but at the beginning of a lambda- or let-body is in every aspect equivalent to set!.
[5.2.2] define-values may be used in internal definitions if the R5RS macro system is not used.
[6] Chicken provides numerous non-standard procedures. See the manual sections on library units for more information.
[6.3.4] User defined character names are supported. See char-name.
[6.3.5] Chicken supports special characters preceded with a backslash ``'' in quoted string constants. n denotes the newline-character, r carriage return, b backspace, t TAB and xXX a character with the code XX in hex.
[6.4] force called with an argument that is not a promise returns that object unchanged. Captured continuations can be safely invoked inside before- and after-thunks of a dynamic-wind form and execute in the outer dynamic context of the dynamic-wind form.
[6.5] The second argument to eval is optional and defaults to the value of (interaction-environment). scheme-report-environment and null-environment accept an optional 2nd parameter: if not #f (which is the default), toplevel bindings to standard procedures are mutable and new toplevel bindings may be introduced.
[6.6.1] if the procedures current-input-port and current-output-port are called with an argument (which should be a port), then that argument is selected as the new current input- and output-port, respectively. The procedures open-input-file, open-output-file, with-input-from-file, with-output-to-file, call-with-input-file and call-with-output-file accept an optional second (or third) argument which should be one or more keywords, if supplied. These arguments specify the mode in which the file is opened. Possible values are the keywords #:text, #:binary or #:append.