MODULE ::= INSTR*
INSTR ::=
| EXPR semicolon
| ASSIGN semicolon
| ASSIGN_IF semicolon
| ASSIGN_ADD semicolon
| CMD_CALL semicolon
| CMD_DEF

ASSIGN ::= ident assign EXPR
ASSIGN_IF ::= ident assign_if EXPR
ASSIGN_ADD ::= ident assign_add EXPR
CMD_CALL ::= ident EXPR*
CMD_DEF ::= command ident colon EXPR* rarrow EXPR* BLOCK
BLOCK ::= obrace INSTR* cbrace
EXPR ::= LITERAL
LITERAL ::= 
| BUILTIN 
| ARRAY 
| ident
BUILTIN ::= 
| bool 
| float 
| int
| string
| symbol

ARRAY ::= osquare EXPR* csquare