Flow

IF

if s == 'foo'
    print 'foo'
elsif s == 'bar'
    print 'bar'
else
    print 'baz'
end

Unless

unless s == 'foo'
    print 's is not foo'
else
    print 's is foo'
end

Case

case S
when 'foo', 'goo'
    print 'was foo or goo'
when 'moo'
    print 'was moo'
else
    print 'was something weird'
end

Loops

for i in 0..3
    print "i is #{i}"
end

Normal While condition

while i < 3
    print "i is #{i}"
end

While modifier

begin
    print "i is #{i}"
    i = i + 1
end while i < 3

Until

until i > 3
    print "i is #{i}"
end

Until with modifier

begin
    print "i is #{i}"
end untill i > 3

Each

(0...3).each do |i|
    print "i is #{i}"
end

Messing with loops

next -- skip the next loop iteration
redo -- run the loop again without checking the loop condition.
break -- exits a loop immediatly

I'll get to this some day