Ruby if, else, unless 문

if conditional [then]
	code ...
[elseif conditional [then]
	code...]...
[else
	code...]
end

x = 1
if x > 2
    puts "x is greater than 2"
elsif x <2 and x != 0
    puts "x is 1"
else
    puts "I can't guess the number"
end

$val = 2
print "val is 2\n" if $val == 2

File.open("my.pl").each do | line |
    next if line.index('#')
    puts line
end

unless conditional [then]
   code
[else
   code ]
end

$var =  1
print "1 -- Value is set\n" if $var
print "2 -- Value is set\n" unless $var

$var = false
print "3 -- Value is set\n" unless $var

case expression
[when expression [, expression ...] [then]
   code ]...
[else
   code ]
end

$age =  5
case $age
when 0 .. 2
    puts "baby"
when 3 .. 6
    puts "little child"
when 7 .. 12
    puts "child"
when 13 .. 18
    puts "youth"
else
    puts "adult"
end

little child