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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def create_path_env_var(new_entries, env=None, env_var='PATH', delimiter=':', prepend=False):
 """Join path entries, combining with an environment variable if specified."""

  if env is None:
    env = {}

  prev_path = env.get(env_var, None)
  if prev_path is None:
    path_dirs = list()
  else:
    path_dirs = list(prev_path.split(delimiter))

  new_entries_list = list(new_entries)

  if prepend:
    path_dirs = new_entries_list + path_dirs
  else:
    path_dirs += new_entries_list

  return delimiter.join(path_dirs)