The part generation code can be condensed a little through use of a regex:

use strict;
use warnings;

my $n = shift;
my $text = do {local $/; <DATA>};

$text =~ s/\n/ /g;

my @lines = $text =~ /(.{1,$n})\s+/g;

print "$_\n" for @lines;

__DATA__
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which generates the same output given the same input as the sample above.