he first
capturing parenthesis in the regular expression that matched, and so
on.  When a <B>default</B> branch is taken, the variable will have the
empty list written to it.  This option may be specified at the same
time as the <B>-indexvar</B> option.
<P><DT><A NAME="M10"><B>-indexvar</B> <I>varName</I></A><DD>
This option (only legal when <B>-regexp</B> is also specified)
specifies the name of a variable into which the list of indices
referring to matching substrings
found by the regular expression engin