Valid ruby syntax

gistfile1.txt

1.9.3p0 :001 > % % % % % 
 => "%" 
1.9.3p0 :002 > % % % % % % % % % % % 
 => "%" 
1.9.3p0 :003 > !?!??!:?!
(irb):70: warning: string literal in condition
 => "!" 
1.9.3p0 :004 > % . . * 0
 => ""
1.9.3p0 :005 > 0_0
 => 0 

gistfile2.txt

irb(main):011:0> class O; def O; end; end; o=O.new
=> #<O:0x007ffd2b1f2838>
irb(main):012:0> (o.O)
=> nil
irb(main):023:0> -_-_-_-_
=> -0.0
irb(main):025:0> Oo=1; oO=2
=> 2
irb(main):026:0> (Oo..oO)
=> 1..2