use strict;
use warnings;

while ( my $string = <DATA> ) {
    chomp $string;
    my ( @stringlets ) = $string =~ 
        m/(?:.{0,40}(?:\s|$))|(?:\S{40})/gs;
    print "$_\n" foreach @stringlets;
    print "\n\n";
}

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