#!/bin/sh

names=$( printf '%s\n%s\n%s\n' "a-webm.webm" "scooby-opustrophic-mystery.opus" "waves.wav" )

printf '%s\n' $names | while read -r line
do
	case $line in
		*.webm)
			line=${line%%.webm}.mkv
		;;
		*.opus)
			line=${line%%.opus}.wv
		;;
		*.wav)
			line=${line%%.wav}.wv
		;;
	esac

	echo $line
done