I have the following code:

...
sub setImage {
    my $self=shift;
    my $filename=shift;
    unless(-r $filename) {
        warn "File $filename not found";
        return;
    }
    my $imgn=shift;
    my $operation=&URI::Escape::uri_escape_utf8(
        (shift) ? "???????! (Delete)" : "?????????! (Store)");
    my $FH=&::File::open($filename, 0, 0);
    my $image;
    # &utf8::downgrade($image);
    sysread($FH, $image, 102400, 0);
    close $FH;
    my $imginfo=eval{&Image::Info::image_info(\$image)};
    if($@ or $imginfo->{"error"}) {
        warn "Invalid image: ".($@ || $imginfo->{"error"});
        return undef;
    }
    my $fields=[
        DIR       => $self->url("fl"),
        OPERATION => $operation,
        FILE_NAME => ".photo$imgn",
        # FILE      => [$filename],
        FILE      => [undef, "image.".$imginfo->{"file_ext"},
            # Content_Type => $imginfo->{"file_media_type"},
            # Content_Type => 'application/octet-stream',
            Content      => $image,
        ],
    ];
    my $response=&ZLR::UA::post(
        &ZLR::UA::absURL("/cgi-bin/file_manager")."",
        $fields,
        Content_Type => "form-data",
    );
    print $response->decoded_content;
}
...

When I try to use function setImage it fails with error HTTP::Message content must be bytes at /usr/lib64/perl5/vendor_perl/5.8.8/HTTP/Request/Common.pm line 91. Worse that I can't reproduce this error without using all of my code and upgrading libwww-perl does nothing. What can cause it?