Calling return in a block can have slightly subtle consequences. Here are some tests with comments that show how it works.

gistfile1.rb

require 'minitest/autorun'

# Show what return in a block does to return values and code after the block is run
class TestReturn < Minitest::Unit::TestCase

  def setup
    @post_code_run = false
  end

  # Method under test
  # Calls a block, then returns its argument times 2
  def yields_and_returns_arg(return_value)
    yield
    @post_code_run = true
    return_value*2
  end

  # Helper to call the above method with a return in the block
  def call_with_return_in_block(return_value_normal, return_value_block)
    yields_and_returns_arg(return_value_normal) { return return_value_block }
  end

  # Tests

  # Ordinarily the code after the yield is run and the return value is 
  # set by the last statement in the function
  def test_block_ordinary_return
    ret = yields_and_returns_arg("xxx") { 123 }
    assert @post_code_run
    assert_equal "xxxxxx", ret
  end

  # BUT if your block calls return, then no code after the yield is run
  # and the return value of your function is automatically the return value
  # of the block.
  def test_block_changes_return
    ret = call_with_return_in_block("xxx", 123)
    assert !@post_code_run
    assert_equal 123, ret
  end
end

# Now let's look at how this all interacts with rescue, else and ensure blocks
#
# An else block is run if (there is no error thrown by the function AND if the
# block did not return).
# BUT does an else block get run if a block calls return? Let's find out.
class TestElseWithReturn < Minitest::Unit::TestCase
  def setup
    @error_block_called  = false
    @else_block_called   = false
    @ensure_block_called = false
  end

  # Method under test
  def yields_and_returns_arg(return_value)
    yield
    return_value*2
  rescue Object => e
    @error_block_called = true
    error_value = "error_return_value"
  else
    @else_block_called = true
    "else_return_value"
  ensure
    @ensure_block_called = "ensure_block_value(error_value = #{error_value})"
  end

  # Helper
  def call_with_return_in_block(return_value_normal, return_value_block)
    yields_and_returns_arg(return_value_normal) { return return_value_block }
  end

  # Tests

  # Ordinarily both else and ensure blocks are run, and the return value
  # is the value from the else block.
  def test_ordinary_return_value
    ret = yields_and_returns_arg("xxx") { 123 }
    assert_equal "else_return_value", ret
    assert !@error_block_called
    assert @else_block_called
    assert @ensure_block_called
  end

  # If there is an error, the error block is run, the else block is not, and the
  # return value is the value of the error block.
  def test_error_block_catches_and_returns_rescue_value
    ret = yields_and_returns_arg("xxx") { raise }
    assert_equal "error_return_value", ret
    assert @error_block_called
    assert !@else_block_called
    assert @ensure_block_called
  end

  # If there is an error in the block: the else block is not run, the error block
  # is run, and the return value is the value of the error block. 
  #
  # Additionally, when the ensure block is run (as it always is), it has access to 
  # variables set in the ensure block, which can be useful.
  def test_ensure_runs_with_error_and_has_access_to_error_variables_and_returns_error_value
    ret = yields_and_returns_arg("xxx") { raise }
    assert_equal "error_return_value", ret
    assert @error_block_called
    assert !@else_block_called
    assert_equal "ensure_block_value(error_value = error_return_value)", @ensure_block_called
  end

  # When the block returns, the error block is not run, the *else block is also not run*,
  # and the return value is the return value of the block. Variables set in the error block
  # (which did not run) are set to nil in the ensure block.
  def test_else_doesnt_run_when_block_returns_and_returns_block_return_value
    ret = call_with_return_in_block("xxx", 123)
    assert_equal 123, ret
    assert !@error_block_called
    assert !@else_block_called
    assert_equal "ensure_block_value(error_value = )", @ensure_block_called
  end

end