for x in true; do
    cat <<EOF;
here doc
EOF
done;
for x in true; do
    for y in true; do
        cat <<EOF;
here doc
EOF
        true;
    done;
done;
while true; do
    cat <<EOF;
here doc
EOF
done;
while true; do
    while true; do
        cat <<EOF;
here doc
EOF
        true;
    done;
done;