$ shellcheck word-lookup.sh

In word-lookup.sh line 31:
regex=$'"definition":"\K(.*?)(?=")'
      ^---------------------------^ SC2039: In POSIX sh, $'..' is undefined.


In word-lookup.sh line 33:
separatedDefinition=$(sed ':a;N;$!ba;s/\n/\n\n/g' <<< "$definitions")
                                                  ^-^ SC2039: In POSIX sh, here-strings are undefined.

For more information:
  https://www.shellcheck.net/wiki/SC2039 -- In POSIX sh, $'..' is undefined.