while (<INFILE>) {
    local $" = ', ';
    my @positions;
    push @positions, pos() while /\000/g;
    print 'Found nulls at line ',
          $. ,
          ', positions '
          "@positions.$/"
        if @positions;
}
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$. is the line number maintained by the diamond operator. $" is the record seperator for stringified arrays. pos() is the last match position maintained by the regex engine.

After Compline,
Zaxo