Note that you try to chroot twice:

  chroot('/var/www/html') or die " chroot() a échoué : $!\n";
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and

  chroot($docroot) or die " chroot() a échoué : $!\n";
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This probably is not what you want. Also, be careful about chroot. You may want to add a chdir as well. From the documentation:

(It doesn't change your current working directory, which is unaffected.)

Lastly, chroot changes root. You should not try to open $docroot$file, just $file.