+ # if the errexit flag is set, unset it until this function returns
+ # otherwise, the shift calls below will abort the program if optional arguments are not supplied
+ if [ -o errexit ]; then
+ set +e
+ trap 'set -e' RETURN
+ fi
+ # $__returnvar has the nameref attribute set, which means it is a reference
+ # to another variable that is passed in as the first argument to this function.
+ # see https://www.gnu.org/software/bash/manual/html_node/Shell-Parameters.html