Reference Documentation for option-ref

Scheme Procedure: option-ref options key default

Search options for a command line option named key and return its value, if found. If the option has no value, but was given, return #t. If the option was not given, return default. options must be the result of a call to getopt-long.

option-ref always succeeds, either by returning the requested option value from the command line, or the default value.

The special key '() can be used to get a list of all non-option arguments.