use strict;
use Fcntl;

my %headers = (
	0  => "file-type", 
    1  => "file-size-in-bytes",    
	2  => "must-be-0",        
	3  => "must-be-0",          
	4  => "offset-to-raster-in-bytes",            
	5  => "size-of-following-header-in-bytes", 
	6  => "width-in-pixels",            
	7  => "height-in-pixels",           
	8  => "device-planes",               
	9  => "bits-per-pixel",              
	10 => "type-of-compression",        
	11 => "raster-size-in-bytes",         
	12 => "horizontal-pixels-per-meter", 
	13 => "vertical-pixels-per-meter",   
	14 => "number-of-colors-used",       
	15 => "number-of-important-colors",
);

my $x = binary_contents("path/to/bitmap.bmp");

my @x = bmp_headers($x);

for my $i(0..$#x){
    printf "%-5s %-10s %-20s\n",$i,$x[$i],$headers{$i}
}

sub bmp_headers {
    # careful - 's' is endian sensitive
    my $t = 'a2Vn2V4s2V6';
    my $x = shift;
    unpack($t,$x);
}

sub binary_contents {
    my $g = shift;
    sysopen(my $F, $g, O_RDONLY) or die "cant open: $g\n$!\n";
    sysread($F, my $x, -s($g));
    close $F;
    return $x;
}



##</code><code>##

open(my $FH, '>:raw', 'path/to/my/new/cool/bitmap.bmp');
print $FH $my_carefully_packed_binary_data