$width=80;
$_ = join "", <STDIN>;

while(length > $width || /\n/){
(s%^(.{1,$width})\n%%) or # wrap at newline
s%^(.{1,$width}) +%% or # wrap at space (which will be removed)
s%^(.{1,$width}[,\?\!\./])%% or # wrap at one of,?!./
s%^(.{$width})%%; # wrap exactly at the edge of the screen
push @lines, $1;
}

print "$_\n" for @lines;