if else repeat
while function
for in next
break NULL NA
NA_integer_
NA_real_
NA_complex_
NA_character_

----------------------------------------------------

[
	["keyword", "if"], ["keyword", "else"], ["keyword", "repeat"],
	["keyword", "while"], ["keyword", "function"],
	["keyword", "for"], ["keyword", "in"], ["keyword", "next"],
	["keyword", "break"], ["keyword", "NULL"], ["keyword", "NA"],
	["keyword", "NA_integer_"],
	["keyword", "NA_real_"],
	["keyword", "NA_complex_"],
	["keyword", "NA_character_"]
]

----------------------------------------------------

Checks for all keywords.