After adding my $buff, Your script work fine here (iceweasel (firefox in debian)) with both PNG and jpg I suppose you can capture network traffic with wireshark or similar and see what happens (or if it is a IE issue??) Regards

#!/usr/bin/perl

use strict;

print "Content-type: image/jpg\n\n";

my $file_name = "/path/to/picture.jpg";
my $buff;

binmode IMAGE;
binmode STDOUT;

open IMAGE, $file_name or die "ERROR $!";
while(read IMAGE, $buff, 1024) {
        print STDOUT $buff;
}
close IMAGE;

1;
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