$fh1 = &file_lock("$folder/index.html");
&file_unlock($fh1);

sub file_lock {
    my $fhandle;
    my $fpath = (shift) . '.lock';
    open($fhandle, ">$fpath");
    flock($fhandle, 2);
    return [$fhandle, $fpath];
}

sub file_unlock {
    my $inp = shift;
    my ($fhandle, $fpath) = @$inp;
    flock($fhandle, 8);
    close($fhandle);
    unlink($fpath);
}