LC_ALL=en_US
unset LC_ALL
unset LANG
export LC_ALL=C
export LANG=C
set +o posix
# attempting to source a non-existant file is not an error...
. /tmp/source-notthere
echo after bad source 1
set -o posix
# ...unless you're in posix mode
. /tmp/source-notthere
echo after bad source 2