Just like sed is a stream editor, ted is a token list editor. The ted package provides two user macros: \Substitute and \ShowTokens. The first is maybe the most useful: it performs substitutions in token lists (even inside braces). The second displays each token of the list (one per line) with its catcode (in the list, not just the current one), and can be useful for debugging or for TeX learners. Ted is designed to work well even if strange tokens (that is, unusual {charcode, catcode} pairs or tokens with a confusing meaning) occur in the list.