I've added Sparklines to the latest version Excel::Writer::XLSX.

Sparklines are small charts showing trends that fit in a single cell. They were invented (or at least named) by Edward Tufte.

In Excel they look something like this:

Excel::Writer::XLSX now provides an interface to Sparklines in Excel and to all of their options to allow worksheets like the following (taken from the output of one of the example programs):

On a related note, I also recently added Excel "Tables" to Excel::Writer::XLSX. Excel Tables are a way of grouping a range of cells into a single entity that has common formatting or that can be referenced from formulas: