0.02 2019-12-21
  - sort data keys in du, dw output.
  - remove "$VAR1 = " from du, dw output.
  - remove no needed indent. indent width become 2.
  - add warnings line number and file name to du, dw output.
  - add dn function. This function is similar as du, dw, but don't encode data.
  - don't send __WARN__ signal. only print dump data to STDERR.
0.01 2019-11-09

  - First release.