Large subject.

Could you tell me why the NoMethodError is happening? I'm using Ruby 2.1.2
in Ubuntu 14.04.

Thanks in advance!

2.1.2 :020 > A = 'A'
 => "A"
2.1.2 :021 > B = 'B'
 => "B"
2.1.2 :022 > 'A' + 'B'
 => "AB"
2.1.2 :023 > 'A' +'B'
 => "AB"
2.1.2 :024 > A + B
 => "AB"
2.1.2 :025 > A +B
NoMethodError: undefined method `+@' for "B":String
    from (irb):25
    from /home/juanjo/.rvm/rubies/ruby-2.1.2/bin/irb:11:in `<main>'
2.1.2 :026 > A +'B'
NoMethodError: undefined method `+@' for "B":String
    from (irb):26
    from /home/juanjo/.rvm/rubies/ruby-2.1.2/bin/irb:11:in `<main>'
2.1.2 :027 > 'A' +B
 => "AB"
2.1.2 :028 > a = 'a'
 => "a"
2.1.2 :029 > a +'B'
 => "aB"

Greets!

-- 
Juanjo Conti
blog: http://www.juanjoconti.com.ar