a few comments:

• try $b->{debug} = 1; between 'new' and 'brand' lines ... anything useful?
• note you should probably pass a format=>'jpg' param as well (happens to default to jpg)
• is the target really 'xjpg' or should that be 'x.jpg'? maybe w/o an extension Image::Magick can't figure it out?
• Do you have the proper libs installed? Can you use straight IM code (two new/Read's and a Composite) and does that work?

       use Image::Magick;
       my $image = Image::Magick->new();
       $image->ReadImage( 'x.jpg' );     
       my $pic = Image::Magick->new();
       $pic->ReadImage( 'x.gif' );
       $pic->Scale( width=>$w, height=>$h );
       $image->Composite( image=>$pic, x=>$x, y=>$y, compose=>'Over' );
       $image->Write( 'xb.jpg' );
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• note that Image::Magick::Brand is just a very simple (and limited) wrapper around the Composite() method so if the problem is there it's easy enough to just not use it .. (see above item for code)

Also, using Imager may be an alternative:

        use Image;
        my $image = Imager->new;
        $image->read(file=>'x.jpg', type=>'jpeg') or die "Cannot read:
+ ", $image->errstr;
        my $pic = Imager->new;
        $pic->read(file=>'x.gif', type=>'gif') or die "Cannot read: ",
+ $pic->errstr;
        $image->paste( left=>$x, top=>$y, img=>
          $pic->scale( xpixels=>$w, ypixels=>$h, type=>'min' ),
         );
        $image->write(file=>"xb.jpg");
[download]