one-at-a-time: shell_variable is 'second'
echo "prefixes: ignore errors"; exit 13
prefixes: ignore errors
*** Error code 13 (ignored)
prefixes: no echo
prefixes: always, no echo
shell-e-option: before
shell-e-option: after
echo 'do-prefix-plus: a regular command'
echo 'do-prefix-plus: prefixed by plus'
do-prefix-plus: prefixed by plus
echo 'do-prefix-plus: a regular command'
{ echo 'do-prefix-plus: a regular command' 
} || exit $?
echo 'do-prefix-plus: prefixed by plus'
do-prefix-plus: prefixed by plus
{ echo 'do-prefix-plus: a regular command' 
} || exit $?
do-error-not-ignored: successful
*** Error code 13 (continuing)

Stop.
make: stopped making "do-error-not-ignored" in unit-tests
exit status 0