Use a capture in your regex

print "[$_]\n"
  for split /(foo)/, 'this foo is foo ... ey';

__output__
[this ]
[foo]
[ is ]
[foo]
[ ... ey]
[download]

Also, split expects a delimiter then a string (and optionally a limit), so passing the result of one split to another can result in unexpected behaviour. See. the split docs for more info on its usage.