use strict;
use warnings;

my $test = '';

while (<DATA>) {
    if (! /^\d+$/) {
        $test .= $_;
        next;
    }
    
    chomp;
    my $n = $_;
    my @words = split /\s+/, $test;
    my @lines;
    
    # Use splice to pull out the desired lines
    push @lines, [splice @words, 0, $n] while @words;
    
    print "@$_\n" for @lines;
}


__DATA__
A huge string separated by lots and lots of words that I'd like to break up
into n shorter strings of length y. This is stored in a __DATA__ section to
make a stand alone test program.

Note that lines containing only a number provide an 'n' like the 10 on the
following line.
10
Note too that you can add more text that will be added and processed by any
subsequent 'n' lines.
12