echo $(echo $(echo 1) + 1) | bc
echo `echo `echo 1` + 1` | bc

echo "Давайте попробуем. Что у нас получилось." | ./convert.rb
Davajte poprobuem. Chto u nas poluchilosj.

$ echo "`echo "`echo 1` + 1" `"
bash: command substitution: line 1: unexpected EOF while looking for matching `"'
bash: command substitution: line 2: syntax error: unexpected end of file
bash: command substitution: line 1: unexpected EOF while looking for matching `"'
bash: command substitution: line 2: syntax error: unexpected end of file
echo 1
$ echo "$(echo "$(echo 1) + 1" )"
1 + 1