TODO

- clean the code: get rid of unnecessary arrays!
- remove precommand style
- add pattern highlight
- expand special characters
- nice feature: separate expansion flags from the parameter, like ${(kv)abc}


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I consider block matching as complete, although some edge cases still don't work, e.g.:

$ echo [ a ] b

Highlights ']' although shouldn't.

$ for ((x=0;x<3;x++)) echo $x; echo Work is done

Highlights and match final 'done' with initial 'for', although shouldn't do neither
Also 'echo' is not highlighted, but that is not related to a block matching part.

$ { for ((x=0;x<3;x++)) echo $x }; echo Work is done

Neither highlight nor match '}' with '{', and treats 'done' as in previous example


Most probably I won't correct these issues.
Parsing command line has some limits: checking each additional condition costs cpu resources (time) and the benefit is marginal.
All typical cases should work correctly.