The package provides a large and sundry set of macros for the manipulation of strings. The macros are developed not merely for cosmetic application (such as changing the case of letters and string substitution), but also for programming applications such as character look-ahead, argument parsing, conditional tests on various string conditions, etc.

The macros were designed all to be expandable (note that things such as \uppercase and \lowercase are not expandable), so that the macros may be strung together sequentially and nested (after a fashion) to achieve rather complex manipulations.