Regexp用于扩展tgz，tar.gz，TGZ和TAR.GZ

Im trying to get a regexp (in bash) to identify files with only the following extensions : tgz, tar.gz, TGZ and TAR.GZ. I tried several ones but cant get it to work. Im using this regexp to select only files files with those extensions to do some work with them : Im trying to get a regexp (in bash) to identify