use strict;
use warnings;

my $partLen = shift
   or die qq{No part length supplied\n};
die qq{Part length not integer\n}
   unless $partLen =~ m{^\d+$};

my $string = q{};
my $wordsFile = q{winter.txt};

open my $wordsFH, q{<}, $wordsFile
   or die qq{open: $wordsFile: $!\n};
{
    local $/;
    $string = <$wordsFH>;
}
close $wordsFH
   or die qq{close: $wordsFile: $!\n};

my @words = split m{\s+}, $string;
my $longestWord =
   ( sort { $b <=> $a } map { length } @words )[0];
die
   qq{Part length too small to accomodate longest word\n}
   if $partLen < $longestWord;

my @parts = ();
my $part = q{};
while ( my $word = shift @words )
{
    $part = $word, next unless $part;
    if ( length($part) + length($word) + 1 > $partLen )
    {
        push @parts, $part;
	$part = $word;
    }
    else
    {
        $part .= qq{ $word};
    }
}
push @parts, $part;

print qq{$_\n} for @parts;