How would you use regex to write functions to do the following:

1. Replace lowercase 'a' with uppercase and vice versa
2. Where words are separated by whitespaces and > and < are special markers, replace >word with word< and vice versa
3. Replace postincrement (i++;) with preincrement (++i;) and vice versa. Variable names are [a-z]+. Input is just a bunch of these statements. Bonus: also do decrement.

Also interested in solutions in other flavors.

Note: this is NOT a homework question. See also my previous explorations of regex:

• Regex split into overlapping strings (Alan Moore's answer is especially instructive)
• Can you use zero-width matching regex in String split? (my solution exploits a known Java regex bug with regards to non-obvious length lookbehind!)