sub shorten {
  local $_ = shift;
  my $len  = shift;
  my $pos;
  
  return $_ if $len >= length;

  $len -= 3;
  $pos = pos while /\w(?=\s)/g && $len >= pos;
  $pos ||= $len;
  substr($_, 0, $pos)."...";
}

print shorten("misunderestimate", 15), "\n";
print shorten("all work and no play makes MeowChow a dull boy", 15), "\n";
print shorten("imapirateiamiam", 15), "\n";

##</code><code>##

  $pos = rindex $_, " ", $len;
  $pos = $len if $pos < 0;