- impl backslash escapes
- eval words
- error handling
- arithmatic
- subst
- standard argv -> name+switches+positionals helper

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older
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- Jest testing
  - endekalogue

test cases:

- intercommand whitespace, blank commands, ;;;,
- braces, nested, escaped, continued newlines, other backslashes, text-after-closing-brace
- trailing whitespace, for commands and scripts
- backslash escapes