The EOL_SPAN_REGEXP rule is similar to the
        EOL_SPAN rule except the match sequence is taken to
        be a regular expression. In addition to the attributes supported by the
        EOL_SPAN tag, the following attributes are
        supported:
HASH_CHAR - a literal string which must
                be at the start of a regular expression.
HASH_CHARS - a list of possible literal
                characters, one of which must match at the start of the regular
                expression.
HASH_CHAR and HASH_CHARS
        attributes are both optional, but you may only specify one, not both. If
        both are specified, HASH_CHARS is ignored and an
        error is shown. Whenever possible, use a literal prefix to specify a
        EOL_SPAN_REGEXP. If the starting prefix is always the
        same, use HASH_CHAR and provide as much prefix as
        possible. Only in rare cases would you omit both attributes, such as the
        case where there is no other reliable way to get the highlighting you
        need, for example, with comments in the Cobol programming
        language.
The regular expression match cannot span more than one line.
Regular expression syntax is described in Appendix E, Regular Expressions.
Here is an EOL_SPAN_REGEXP that highlights
        MS-DOS batch file comments, which start with REM,
        followed by any whitespace character, and extend until the end of the
        line:
<EOL_SPAN_REGEXP AT_WHITESPACE_END="TRUE" HASH_CHAR="REM" TYPE="COMMENT1">REM\s</EOL_SPAN_REGEXP>