fork is making irb unresponsive

gistfile1.rb

# This makes irb sluggish and randomly unresponsive
if fork
  puts "Hello from parent process #{Process.pid}"
else
  puts "Hello from child process #{Process.pid}"
  # I thought the child process would exit automatically here?
end


# This works fine
if fork
  puts "Hello from parent process #{Process.pid}"
else
  puts "Hello from child process #{Process.pid}"
  exit
end

# back to parent irb process