RUBYOPT

Additional command-line options to Ruby; examined after real command-line options are parsed ($SAFE must be 0).

RUBYLIB

Additional search path for Ruby programs ($SAFE must be 0).

RUBYPATH

With -S option, search path for Ruby programs (defaults to PATH).

RUBYSHELL

Shell to use when spawning a process; if not set, will also check SHELL or COMSPEC. DLN_LIBRARY_PATH Search path for dynamically loaded modules.

RUBYLIB_PREFIX

(Windows only) Mangle the RUBYLIB search path by adding this prefix to each component.