Supported features:
* dfns {code}, d-monadic-ops _{code}, d-dyadic-ops _{code}_
⍺ left argument, ⍵ right argument,
⍺⍺ left array operand, ⍶⍶ left function operand, ⍵⍵ right array operand, ⍹⍹ right function operand,
∇ recurse function, _∇ recurse monadic op, _∇_ recurse dyadic op
■ early exit, : guard
⋄ multiple statements
* numbers: . decimal separator, ¯ negative sign, ⏨ exponent notation, ᴊ complex separator
* character literals: 'abc'
* string literals: "abc" with escapes using ⍘
* names: abc array, Abc function, _Abc monadic op, _Abc_ dyadic op
* get ⎕ read evaluated input, get ⍞ read string input, set ⎕ print with newline, set ⍞ print without newline
* array notation: ⟨⋄⟩ vector, [⋄] higher rank array (combine major cells), ‿ tie (like vector notation)
* trains: ⦅⦆ deriving function, _⦅⦆ deriving adverb, _⦅⦆_ deriving conjunction
* structs: ⦃statements⦄, qualified access →
* assignment with ←, modify assignment with ↩, constant assignment with ⇇, private assignment with ↚
* array assignment with array notation of names
* comments: ⍝ until end of line, ⟃⟄ inline
