ruby语言的BUG

mystr = "我爱fd--xbsk伙 d--d 与天2载--r user--fd"
if /--([bxsrgylh]{1,3})(.*)--/ =~ mystr
  puts $1
  puts $2
  g = "<span style='"
  $1.split('').each do |vv|
    puts vv
  end
  puts $2
  puts g
#  g += "'>" + $2 + "</span>"
#  mystr = mystr.sub($&, g)
end
puts '----over'
puts mystr

$2 is null.It is a bug.If I comment

$1.split('').each do |vv|
    puts vv
  end

$2 is OK
gogogo