#!/usr/bin/perl -w
use strict;
use HTML::TokeParser::Simple;

my $total = 0;
my $p = HTML::TokeParser::Simple->new(*DATA);

my $length_left = shift || 40;
my $abstract = "";

my @stack;
while (my $t = $p->get_token) { 
	$_ = $t->as_is;
	
	if ($t->is_text) {
		s/\s+/ /g;
		s/^(.{1,$length_left}\S*).*/$1/s;
		$length_left -= length;
	}
	elsif($t->is_start_tag) {
		push @stack, $t->return_tag;
	}
	elsif($t->is_end_tag) {
		pop @stack if $stack[-1] eq $t->return_tag;
	}
	
	$abstract .= $_;
	last unless $length_left > 0;
}

$abstract .= join '', map "</$_>", reverse @stack;

print $abstract, $/;