A simple-ish fish script for randomly selecting a new Mullvad relay from those available.

mullmix.fish

function mullmix
	# Locally scoped function
	function usage
		echo "$_ - Randomly set a new mullvad relay from the list of available relays"
		echo "Usage: $_ [-h|--help] [COUNTRY]"
		echo "  -h, --help: Display this message"
		echo "  COUNTRY: a two-letter country code, e.g. \"us\". If provided, $_ will only select relays from this country."
		# Delete self to avoid potential conflicts
		functions -e usage
	end

	set -l arg_count (count $argv)
	switch $arg_count
		case 0
			# Default
			set pattern "[a-z]{2}-[a-z]{3}-wg-[0-9]{3}"
		case 1
			switch $argv[1]
				case '-h' '--help'
					usage
					return 0
				# COUNTRY code provided
				case '*'
					set pattern "$argv[1]-[a-z]{3}-wg-[0-9]{3}"
			end
		case '*'
			echo "Error: Unexpected extra arguments"
			usage
            		return 1
	end

	# Select a hostname
	set relay_hostnames (mullvad relay list | grep -Po "$pattern")
	# Set new relay
	mullvad relay set location (random choice $relay_hostnames)
end