wget http://registry.vibed.org/files/dub-0.9.11-linux-x86_64.gz
gzip -d dub-0.9.11-linux-x86_64.gz
chmod +x dub-0.9.11-linux-x86_64.gz
./dub-0.9.11-linux-x86_64 help

I tried your approach and it worked!

After another look I found that I was downloading the gz file with chromium browser before. and the file sizes are different with the wget one.

So maybe it was because my download was bad. (although I've tried several times, and never had a similar issue)

Thanks for your help :-)

Glad it worked :-) I'll look into the Chrome issue. Maybe there is an
issue with the HTTP headers the server sends or something.