This snippet uses a pure regexp approach to breaking a string up into stringlets of no more than 'n' length, broken on the first whitespace before 'n', OR a hard break at 'n' characters if there is no preceeding whitespace on which to break. Not sure if this is what you're after, but it seems to be a start in the right direction. If you simply want to crop at 'n' or less (depending on whitespace), remove the /g modifier and capture only the first stringlet.

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.
[download]

Applying the "..." elipses is trivial at this point.

I hope this helps... it's late, I may have misread the question. ;)