Use send:

lizzy:/tmp% cat Test1a.rb
class Test1a
    def Test1a.howdy
      return 'Hello, world!'
    end
end
lizzy:/tmp% cat test1
#!/usr/bin/env ruby

require_relative 'Test1a'
myvar = 'howdy'
puts Test1a.send myvar
lizzy:/tmp% ./test1
Hello, world!
lizzy:/tmp%

-- 
Jos Backus
jos at catnook.com