S3 permission setting not being set properly

After $perms is set according to the configuration, it then tries to redefine it using a constant. The problem is that the value in the configuration is 'public-read' which is the value of the constant, not the name, so this causes an error. I suppose this would work if the form values were the constant names instead of the values (i.e. ACL_PUBLIC_READ), but I don't see why its necessary.

Removing that line seems to work as it should.

Patch attached.