When writing the script posted in this reply I originally tried to use unpack to extract each line after sorting but it mashed the output into a single line with no line feeds. (I went with substr instead). The documentation states that unpack does the reverse of pack but using the 'A' template seems to lose trailing newline characters when unpacking. Embedded newlines are preserved. Using the 'a' template instead works as expected.

use strict;
use warnings;

use feature    qw{ say };
use List::Util qw{ max };

my $string   = qq{abc\n};
my $packed   = pack   q{A*}, $string;
my $unpacked = unpack q{A*}, $packed;

say
   $string eq $packed
   ? q{OK - original and packed are the same}
   : q{Not OK - original and packed differ};

sideBySide( $string, $packed );

say
   $string eq $unpacked
   ? q{OK - original and unpacked are the same}
   : q{Not OK - original and unpacked differ};

sideBySide( $string, $unpacked );

say q{=} x 50;

$string  .= qq{def\n};
$packed   = pack   q{A*}, $string;
$unpacked = unpack q{A*}, $packed;

say
   $string eq $packed
   ? q{OK - original and packed are the same}
   : q{Not OK - original and packed differ};

sideBySide( $string, $packed );

say
   $string eq $unpacked
   ? q{OK - original and unpacked are the same}
   : q{Not OK - original and unpacked differ};

sideBySide( $string, $unpacked );

sub sideBySide
{
    my( $original, $modified ) = @_;

    my @origChars = map { sprintf q{%#02x}, ord } split m{}, $original
+;
    my @modChars  = map { sprintf q{%#02x}, ord } split m{}, $modified
+;
    my $nRows     = max scalar( @origChars ), scalar( @modChars );

    for ( 1 .. $nRows )
    {
        printf qq{%8s%8s\n},
           scalar @origChars ? shift @origChars : q{},
           scalar @modChars  ? shift @modChars  : q{};
    }
}

[download]

The output.

OK - original and packed are the same
    0x61    0x61
    0x62    0x62
    0x63    0x63
     0xa     0xa
Not OK - original and unpacked differ
    0x61    0x61
    0x62    0x62
    0x63    0x63
     0xa        
==================================================
OK - original and packed are the same
    0x61    0x61
    0x62    0x62
    0x63    0x63
     0xa     0xa
    0x64    0x64
    0x65    0x65
    0x66    0x66
     0xa     0xa
Not OK - original and unpacked differ
    0x61    0x61
    0x62    0x62
    0x63    0x63
     0xa     0xa
    0x64    0x64
    0x65    0x65
    0x66    0x66
     0xa

[download]

My questions: is this a bugette, a feature, or am I having a senior moment?

Cheers,

JohnGG

In reply to Problem with pack/unpack asymmetry by johngg

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