another return

t.bash

#!/usr/bin/env bash

set -o errexit
set -o nounset
set -o pipefail
shopt -s inherit_errexit

readonly true=1
readonly false=0

return() {
  case $1 in
    0|true)
      echo true ;
      builtin return 0
      ;;
    1|false)
      echo false ;
      builtin return 1
      ;;
    *)
      echo $1 ;
      builtin return $1 ;;
  esac
}

is_success() {
  return false
}

foo() {
  local a
  a=$(is_success)
  echo "$a"
}

foo