import re
stuff = ["$x$y0123", "$", "", "  \t", "$x      @hi"]

p1 = re.compile(r'(?:\$[A-Z_]\w*|\s)*$', re.IGNORECASE)
p2 = re.compile(r'\$[A-Z_]\w*|\s+', re.IGNORECASE)

for thing in stuff:
	if p1.match(thing):
		print(p2.findall(thing))