Here are some examples:

• Copy a spreadsheet and change the clipboard so that it can be pasted into a wiki, with vertical bars (|) instead of tabs
• Modify your multi-line clipboard text so that it can be pasted into Java or Python.
• Modify an URL in the clipboard pointing to Amazon so that it has your Associate ID in it.
• Decompose an URL so that it can be parsed by humans, or Python.
• Run your clipboard through an arbitrary program (like sort) via piping.
• Force the multi clipboard into text only.
• Convert some text into unicode with \unnnn type escapes.
• Print out a variable in python.

It uses wxPython and if you bring it's window to the front your clipboard will be modified according to which modifier is currently selected.

See the wiki for more information.