erb2.3 --version (return code: 0)
erb.rb [2.1.0 $]
erb2.3 -HELP (return code: 1)
print this help
erb2.3 [switches] [var=value...] [inputfile]
-x print ruby script
-n print ruby script with line number
-v enable verbose mode
-d set $DEBUG to true
-r library load a library
-S safe_level set $SAFE (0..1)
-E ex[:in] set default external/internal encodings
-U set default encoding to UTF-8.
-T trim_mode specify trim_mode (0..2, -)
-P ignore lines which start with "%"
var=value set variable