It is possible to have whitespace between the -I command line option and its parameter.
Note that there must be no whitespace between the leading dot and the two characters s and o. Otherwise, only groff interprets the .so request (and soelim ignores it).
|-C||Recognize .so even when followed by a character other than space or newline.|
|-Idir||This option may be used to specify a directory to search for files (both those on the command line and those named in .so lines). The current directory is always searched first. This option may be specified more than once, the directories will be searched in the order specified. No directory search is performed for files specified using an absolute path.|
|-v||Print the version number.|