10 Macros for text handling

There are a number of builtins in m4 for manipulating text in various ways, extracting substrings, searching, substituting, and so on.

• Len: Calculating length of strings
• Index macro: Searching for substrings
• Regexp: Searching for regular expressions
• Substr: Extracting substrings
• Translit: Translating characters
• Patsubst: Substituting text by regular expression
• Format: Formatting strings (printf-like)