use strict;
use warnings;

my $len = 40;
print "0123456789012345678901234567890123456789\n";
while ( my $string = <DATA> ) {
    chomp $string;
    $string =~ 
        s/((?:.{0,$len}(?=\s|$))|(?:\S{$len}))(?:.+$)?/$1.../s;
    print "$string\n";
}

__DATA__
Now is the time for all good men to come to the aid of their country.
Nowisthetimeforallgoodmentocometotheaidoftheircountry.