Regex for localized paths

What can I do to make this regex match '/en/' and '/en'? (edit: as well as '/en/foo') It matches '/en/foo'.

:locales = %w[en ja]
:pa开发者_运维技巧ttern = /^\/?(#{Regexp.union(:locales)})(\/.+)$/

:pattern = /^\/?(#{Regexp.union(:locales)})\/?$/