rubyのswitch文はcaseという

case $age
when 0 .. 2
  "baby"
when 3 .. 6
  "little child"
when 7 .. 12
  "child"
when 13 .. 18
  "youth"
else
  "adult"
end

ネタ元

• http://www.ruby-lang.org/ja/man/html/_C0A9B8E6B9BDC2A4.html#case