Now that brother VSarkiss called my attention to the intent of the code, it could be simplified like this:

for (0..3) {
  print "....\b\b\b\b";
  sleep 1;
}
[download]

or, for the uberterse version:

print "....\b\b\b\b" and sleep 1 for (0..3);
[download]

with brother BUU's caveat that if the print doesn't succeed, the sleep statement won't execute.

Updated: er, actually, that's wrong. There needs to be a sleep after each period.

for (0..3) {
  print "." and sleep 1 for (0..3);
  print "\b\b\b\b" and sleep 1;
}
[download]