can't substitute the matches with the output of a command that takes the match groups as input

I'd like sth like
```
echo 'hello AworldA' | sd 'A(.*)A' './toupper.sh $1'
hello WORLD
```
where `toupper.sh` is any command/program like
```
#!/usr/bin/env bash
echo "$1" | tr a-z A-Z
```