#!/usr/bin/perl
# The Missing Textutils, Ondrej Bojar, obo@cuni.cz
# http://www.cuni.cz/~obo/textutils
#
# 'unwrap' concatenates all lines, inserting a space in between.
# Only blank lines are preserved.
# write than "grep -v '^$'".
#
# $Id: unwrap,v 1.1 2012-10-07 23:12:02 bojar Exp $

use strict;

my $par = "";
while (<>) {
  chomp;
  if (/^\s*$/) {
    # blank line
    print $par, "\n" if $par ne "";
    $par = "";
    print "\n";
  } else {
    $par .= " " if $par ne "";
    $par .= $_;
  }
}
print $par, "\n" if $par ne "";