Lines written to a file are not contiguous

[Sherman Willden]

Lines written to a file are not contiguous.

First I will describe what I want the script to perform and then I
will include the script at the end of this message. I downloaded the
Oreilly Programming Perl Version 4 examples. There are 30 directories
with 2211 files.  I want each chapter to have a consolidated file with
all the examples for that chapter. I created the
consolidate_examples.pl script which goes into each directory, reads
each file, and then writes the files lines to the
consolidated_perl4_examples/<directory name>. An example is
consolidated_perl4_examples/ch00_preface with contains six lines.
ch27_perl_functions is the largest and has 435 files which results in
a single file with 870 lines. What I expected is as follows. If the
first file I read from contains six lines then I expected the
resulting consolidated file to have the first six lines align with
read-from file. But they don't. The consolidated file's lines are
mixed with the first six lines comming from file 1 or file 8 or
whatever. The lines read in are not contiguous. For example in ch12
the first consolidated line comes from file 004 and the second
consolidated line comes from 055.

------------ SCRIPT --------------

#!/usr/bin/perl

use v5.16.3;
# use v5.14.2;
use File::Basename;
use File::Path;

my $base_directory =
"/home/sherman/perl_documentation/programming_perl_4_examples/programming_perl_examples/program_listings";
my $basename_directory = basename($base_directory) || die "Unable to
determine the basename: $!\n";
my $write_directory =
"/home/sherman/perl_documentation/programming_perl_4_examples/consolidated_perl4_examples";
if ( not -e "$write_directory" ) {
    mkdir("$write_directory") || die "Unable to create $write_directory: $!\n";
}

chdir($base_directory) || die "Unable to change directory to
$basename_directory: $!\n";

opendir(PERLDIR, ".") or die "Unable to open $basename_directory: $!\n";
my @docdirs = grep { $_ ne '.' and $_ ne '..' } readdir PERLDIR;
closedir(PERLDIR) || die "Unable to close $basename_directory:$!\n";
foreach my $directory ( @docdirs ) {
    chdir("$base_directory/$directory") || die "Unable to change
directory to $directory: $!\n";
    my $write_file = "$write_directory/$directory";
    opendir(EXAMPLES, ".") or die "Unable to open $directory: $!\n";
    my @docfiles = grep {$_ ne '.' and $_ ne '..'} readdir EXAMPLES;
    closedir(EXAMPLES) || die "Unable to close $directory: $!\n";
    foreach my $file ( @docfiles ) {
        my ( $write, $read );
        open(WRITE, ">>$write_file") || die "Unable to open $write_file: $!\n";
        open(READ, $file) || die "Unable to open $file: $!\n";
        my $line = readline(READ) || die "Unable to read $file: $!\n";
        print WRITE "$line\n";
        close(WRITE) || die "Unable to close $write_file: $!\n";
        close(READ) || die "Unable to close $file: $!\n";
    }
}

1;