*^%Q&$*&^@$&*!^@$*&^&^*&^&

grep -F $'r' application.log

grep -F "$(printf 'r')" application.log

$ printf "arb" | grep -F $'r' | hexdump -c
0000000   a  r   b  n

-F, --fixed-strings
          Interpret PATTERN as a list of fixed strings, separated by newlines, any of which is to be matched.  (-F is specified
          by POSIX.)