In some older versions of bash, when dealing with process substitution, you actually needed the dash. For example get_data | tee >(cmd) get_data | tee

In some older versions of bash, when dealing with process substitution, you actually needed the dash. For example get_data | tee >(cmd) get_data | tee >(cat | cmd) would fail but get_data | tee >(cat - | cmd) would succeed.