+=item --spark[=<glyphs>]
+
+Replace lines by I<sparklines>,
+single characters corresponding to input values.
+A specified sequence of unicode characters will be used for
+Of a specified sequence of unicode characters,
+the first one will be used for non-values,
+the last one for the maximum,
+the second (if any) for the minimum,
+and any remaining will be distributed over the range of values.
+Unspecified, block fill glyphs U+2581-2588 will be used.
+