pattern.rb

def get patterns
  loop do
    s = gets
    p = patterns.find{|p|p=~s}
    return [p, s] if p
  end
end

number = /\d+/
word = /[a-z]+/

pattern, text = get [number, word]
case [pattern]
when [number]
  puts text.to_i+1
when [word]
  puts text.upcase
else
  puts 'what!?'
end

class PatternConverter
  def initialize(pattern, &convert)
    @pattern = pattern
    @convert = convert
  end

  def ===(s)
    @pattern =~ s
  end

  def convert(s)
    @convert[s] if @pattern =~ s
  end
end

converters = [
  PatternConverter.new(/\d+/) {|s| s.to_i + 1 },
  PatternConverter.new(/[a-z]+/) {|s| s.upcase }
]

def get_converted_value(converters)
  loop { gets.tap {|s| converters.find {|c| c === s }.tap {|c| return c.convert(s) if c } } }
end