s|
|\
\
|g
# all <para> to left margin on next line
s|^ *\(<para>.*\)|\
\1|
s|^ *\(</para>.*\)|\1|
# sect's on next line, appropriate indent
s|^ *\(</*sect1.*\)|\
 \1|
s|^ *\(</*sect2.*\)|\
  \1|
s|^ *\(</*sect3.*\)|\
   \1|
s|^ *\(</*sect4.*\)|\
    \1|