use strict;
use warnings;

my $initial_read = 1;

$| = 1;

my $arg = $ARGV[0];
die "usage: $0 [read|readline|sysread]\n" 
   unless @ARGV == 1 && defined $arg 
      && $arg =~ /^(?:read|readline|sysread)\z/;

my $file_name;
$file_name = "d:/sourceforge-4_3-hf5-dl3.zip";

my ($fh, $buf, $rc, $bangn, $bangs, $prt);

open $fh, '<', $file_name or do {
   $bangn=$!+0; $bangs=$!;
   die "Unable to open file $file_name: $bangn: $bangs\n";
};

if ($initial_read) {
   undef $!;
   if ($arg eq "read") {
      $rc = read $fh, $buf, 1;
   } elsif ($arg eq "sysread") {
      $rc = sysread $fh, $buf, 1;
   } else {
      $rc = readline $fh;
   }
   $bangn=$!+0;  $bangs=$!;
   $prt = $arg eq "readline" ? "len=@{[length $rc]}" 
                             : "rc=$rc" if defined $rc;
   print "msg 1: ", defined $rc ? "$prt\n" 
                                : "rc=undef: $bangn: $bangs\n";
}

print("Eject the media then press Enter");
<STDIN>;

my $cnt = 0;
undef $!;
if ($arg eq "read") {
   while ($rc = read $fh, $buf, 100000) { $cnt += $rc; }
} elsif ($arg eq "sysread") {
   while ($rc = sysread $fh, $buf, 100000) { $cnt += $rc; }
} else {
   while (defined($rc = readline $fh)) { $cnt += length $rc; }
}
$bangn=$!+0; $bangs=$!;
$prt = $arg eq "readline" ? "len=@{[length $rc]}" : "cnt=$cnt rc=$rc"
   if defined $rc;
print "msg 2: ", defined $rc ? "$prt\n" 
                             : "cnt=$cnt rc=undef: $bangn: $bangs\n";

close $fh or do {
   $bangn=$!+0; $bangs=$!;
   die "Close failed: $bangn: $bangs\n";
};