I'm a new user of pack, and just getting started with mod_perl.
I'm using this code to send a 1 pixel clear gif under mod_perl:

#!c:\apps\perl\bin\perl.exe

use strict;
my $hex =
    '47494638396101000100e3000000000' .
    '0bf000000bf00bfbf000000bfbf00bf' . 
    '00bfbfc0c0c0808080ff000000ff00f' . 
    'fff000000ffff00ff00ffffffffff21' . 
    'f9040100000f002c000000000100010' . 
    '0400402f045003b';

my $gif = pack("H*",$hex);
binmode(STDOUT);
print "Content-type: image/gif\n";
print "Content-length: 85\n";
print "\n";
print $gif;
[download]

That code above seems to work, and runs instantly on a winnt & indigo perl box.

As I mentioned, I'm a new user of "pack." After reading about pack in perlfunc, I tried specifying the length in the pack statement ('H85') vs. using the star ('H*'), like this:

#!c:\apps\perl\bin\perl.exe

use strict;
my $hex =
    '47494638396101000100e3000000000' .
    '0bf000000bf00bfbf000000bfbf00bf' . 
    '00bfbfc0c0c0808080ff000000ff00f' . 
    'fff000000ffff00ff00ffffffffff21' . 
    'f9040100000f002c000000000100010' . 
    '0400402f045003b';

my $gif = pack("H85",$hex);
binmode(STDOUT);
print "Content-type: image/gif\n";
print "Content-length: 85\n";
print "\n";
print $gif;
[download]

This second version runs extremely slowly on the same system, taking 3 or 4 seconds to load the (invisible) image.

• Why do these two program have such different run times?
• Is the 'H85' pack wrong? If so, why?
• And, in general, am I going about this (dynamically generating a clear single pixel gif) the right way?

Many thanks
nop

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