my $pixellist = '9347248,9347248,9413041';

my @allpixels = split( /,/ , $pixellist );

my $newblob = reverse pack "(VX)*", reverse @allpixels;
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Well, I'm not suggesting that this is faster than the original or that you use it; I just wanted to prove that you can omit the entire for-loop if you make your pack command sufficiently unreadable ;-)