The urlencode function from the manual does "Returns a string in which all non-alphanumeric characters except -_. have been replaced with a percent (%) sign followed by two hex digits and spaces encoded as plus (+) signs."

When working on a local file system converting spaces in filenames to %20 for passing to separate programs is favourable to the conversion to a plus sign. Either a change of functionality to convert spaces to %20 instead of +, or an option to specify the behaviour would be nice.