CGI::QueryExtension#[]

# File tmp/rubies/ruby-3.3.0/lib/cgi/core.rb, line 714
def [](key)
  params = @params[key]
  return '' unless params
  value = params[0]
  if @multipart
    if value
      return value
    elsif defined? StringIO
      StringIO.new("".b)
    else
      Tempfile.new("CGI",encoding: Encoding::ASCII_8BIT)
    end
  else
    str = if value then value.dup else "" end
    str
  end
end