#! perl -slw
use strict;

our $N ||= 16;

my $longstring = do{ local $/; <DATA> };

for my $n ( map{ $_*50 } 4 .. $N ) {
    my $cutoff1  = 1+rindex $longstring, '<', $n;
    my $cutoff2 = length $1 if $longstring =~ m[^(.{0,$n}[\.,:;!?])]s;
    my $cutoff3 = 1+rindex $longstring, ' ', $n;
    my $cutoff = $cutoff1 > ( $n - 25 ) ? $cutoff1
               : $cutoff2 > ( $n - 25 ) ? $cutoff2
               : $cutoff3;
    my $substring = substr $longstring, 0, $cutoff-1;
    print "\n$n($cutoff)\n'$substring'";
}


__DATA__
<p>
Welcome to the Perl Monastery.  We hope your stay is long 
and enjoyable.  You are probably wondering what PerlMonks 
is all about. Hopefully this page will answer some of those 
questions.
</p><p>
<b>What Perl Monks is:</b><br />
<li>Our attempt to make learning Perl as nonintimidating 
and easy to use as possible
<li>A place for you and others to polish, improve, and 
showcase your Perl skills
<li>A community which allows everyone to grow and learn 
from each other.
</p>
<p><b>Areas within the monastery:</b></p>
<ul>
<p><li><a href="/index.pl?node=Seekers%20of%20Perl%20Wisdom">Seekers o
+f Perl Wisdom</a>-The place you can go when 
you have got a question on how to do something or are 
unsure why something just isn't working.  Then other monks 
can offer you their wisdom and suggestions.  
</p>
[download]

Output:

P:\test>junk -N=8

200(199)
'<p>
Welcome to the Perl Monastery.  We hope your stay is long
and enjoyable.  You are probably wondering what PerlMonks
is all about. Hopefully this page will answer some of those
questions.
</p>'

250(236)
'<p>
Welcome to the Perl Monastery.  We hope your stay is long
and enjoyable.  You are probably wondering what PerlMonks
is all about. Hopefully this page will answer some of those
questions.
</p><p>
<b>What Perl Monks is:</b><br />
'

300(297)
'<p>
Welcome to the Perl Monastery.  We hope your stay is long
and enjoyable.  You are probably wondering what PerlMonks
is all about. Hopefully this page will answer some of those
questions.
</p><p>
<b>What Perl Monks is:</b><br />
<li>Our attempt to make learning Perl as nonintimidating
and'

350(345)
'<p>
Welcome to the Perl Monastery.  We hope your stay is long
and enjoyable.  You are probably wondering what PerlMonks
is all about. Hopefully this page will answer some of those
questions.
</p><p>
<b>What Perl Monks is:</b><br />
<li>Our attempt to make learning Perl as nonintimidating
and easy to use as possible
<li>A place for you and'

400(396)
'<p>
Welcome to the Perl Monastery.  We hope your stay is long
and enjoyable.  You are probably wondering what PerlMonks
is all about. Hopefully this page will answer some of those
questions.
</p><p>
<b>What Perl Monks is:</b><br />
<li>Our attempt to make learning Perl as nonintimidating
and easy to use as possible
<li>A place for you and others to polish, improve, and
showcase your Perl'
[download]