Not sure about other systems, but many Unix terminals support a backspace character (chr(8)) to step back one, so you can space out a message by repeatedly printing backspace, space, backspace something like this:

my $clear = "\x08 \x08";
while (not $finished) {
  my $string = status();
  print $string;   # without a newline!
  do_more_stuff();
  print $clear x length($string);
}
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