old_contents: EXP = 'EXP'
  VAL = 'VAL'
  ENV = 'ENV'
  UNEV = 'UNEV'
  FUNC = 'FUNC'
  ARGL = 'ARGL'
  CONT = 'CONT'
  CURR = 'CURR'
  
  STACK = 'STACK'
new_contents: # register shorthand
  EXPR = 'EXPR'
  VAL = 'VAL'
  ENV = 'ENV'
  UNEV = 'UNEV'
  FUNC = 'FUNC'
  ARGL = 'ARGL'
  CONT = 'CONT'
  CURR = 'CURR'
  
  STACK = 'STACK'
  
  def fetch(reg):
  	with open(reg, 'r') as regf:
  		return regf.read()
  
  def assign(src, dst):
  	with open(src, 'r') as srcf, open(dst, 'w') as dstf:
  		dstf.write(srcf.read())
subject: Add fetch and assign