G'day stevieb,

I don't have MSWin available, but I can fake it sufficiently for this test with:

use open IO => ':crlf';
[download]

Here's four ways to do what you want (plus a fifth just to show what happens when one of those isn't used). There may, of course, be other ways I didn't think of.

#!/usr/bin/env perl -l

use strict;
use warnings;
use autodie;
use open IO => ':crlf';

my ($f, $fh); 
my $mf = \$f;
my $test_file = 'pm_1144333_test_file.txt';

open $fh, '>', $mf;
print $fh 'hello';
close $fh;
print_raw_1('mem:  ', $mf);
print_raw_2('mem:  ', $mf);
print_raw_3('mem:  ', $mf);
print_raw_4('mem:  ', $mf);
print_raw_5('mem:  ', $mf);

open $fh, '>', $test_file;
print $fh 'hello';
close $fh;
print_raw_1('file: ', $test_file);
print_raw_2('file: ', $test_file);
print_raw_3('file: ', $test_file);
print_raw_4('file: ', $test_file);
print_raw_5('file: ', $test_file);


sub print_raw_1 {
    my ($prompt, $file) = @_;

    open my $fh, '<:raw', $file;
    print '1. ', $prompt, unpack 'H*' while (<$fh>);
    close $fh;
}

sub print_raw_2 {
    my ($prompt, $file) = @_;

    open my $fh, '<', $file;
    binmode $fh, ':raw';
    print '2. ', $prompt, unpack 'H*' while (<$fh>);
    close $fh;
}

sub print_raw_3 {
    my ($prompt, $file) = @_;

    use open IN => ':raw';
    open my $fh, '<', $file;
    print '3. ', $prompt, unpack 'H*' while (<$fh>);
    close $fh;
}

sub print_raw_4 {
    my ($prompt, $file) = @_;

    use open IO => ':raw';
    open my $fh, '<', $file;
    print '4. ', $prompt, unpack 'H*' while (<$fh>);
    close $fh;
}

sub print_raw_5 {
    my ($prompt, $file) = @_;

    open my $fh, '<', $file;
    print '5. ', $prompt, unpack 'H*' while (<$fh>);
    close $fh;
}
[download]

Here's the output:

1. mem:  68656c6c6f0d0a
2. mem:  68656c6c6f0d0a
3. mem:  68656c6c6f0d0a
4. mem:  68656c6c6f0d0a
5. mem:  68656c6c6f0a
1. file: 68656c6c6f0d0a
2. file: 68656c6c6f0d0a
3. file: 68656c6c6f0d0a
4. file: 68656c6c6f0d0a
5. file: 68656c6c6f0a
[download]

And, if I hadn't "faked it", i.e. not including the use open IO => ':crlf'; line, I just get:

1. mem:  68656c6c6f0a
2. mem:  68656c6c6f0a
3. mem:  68656c6c6f0a
4. mem:  68656c6c6f0a
5. mem:  68656c6c6f0a
1. file: 68656c6c6f0a
2. file: 68656c6c6f0a
3. file: 68656c6c6f0a
4. file: 68656c6c6f0a
5. file: 68656c6c6f0a
[download]

See also:

• the open function
• the open pragma
• PerlIO

and, if you're interested in internals:

• perliol - C API for Perl's implementation of IO in Layers
• perlapio - perl's IO abstraction interface

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