Automatically switch default route to secondary uplink when primary uplink is unavailable

Hello, I have dark fibre with a static ip and a DSL line behind a NAT box. I would like to have the default route on the dark fibre and switch to the DSL line when the dark fibre is unavailable. I determine if the line is available by ping 1.1.1.1 and 8.8.8.8. I implemented the above in perl, but wonder if I reimplemented the wheel and this is already possible with frr, bird or another piece of software on Linux? Here I don't have BGP available. Find my perl Daemon here (public IPs changed), it runs every minute by cron. https://tg.st/u/genericrouteswitcher.pl Cheers, Thomas