echo x1 | ( cat & wait )
echo x1a | ( :& cat & wait )

echo x2 | for f in 1; do
	cat & wait
done
echo x2a | if true; then cat & wait; fi
echo x2b | for (( i=0; i < 1; i++ )) ; do cat & wait; done

echo x3 | { cat & wait; }

lambda() { cat & wait; }
echo x3a | lambda

: ${TMPDIR:=/tmp}
SRCF=$TMPDIR/bash-src-$$
cat > $SRCF << \EOF
cat & wait
EOF
echo x3b | . $SRCF
rm -f $SRCF