Unless
puts "x" unless 1==2
#=> x
unless 1==2
puts "x"
end
#=> x
# unless one equal to two is TRUE, otherwise output x
# same as
if not 1==2
puts "x"
end
# => x
# if one equal to two is NOT TRUE, then output x
puts "y" unless 1==1
#=> nil
unless 1==1
puts "x"
end
#=> nil
# unless one equal to one is TRUE, otherwise output x
If vs Unless
print 1 if true
#=> 1
print 1 unless false
#=> 1