Nim base64 encode and validated decode

import std/[base64, strutils]

proc tryDecode(s: string): string =
  let compact = s.strip()
  if compact.len mod 4 != 0:
    return "invalid base64: length not a multiple of 4"
  try:
    result = decode(compact)
  except ValueError as e:
    result = "invalid base64: " & e.msg

echo encode("hello, Nim")
echo tryDecode("aGVsbG8=")
echo tryDecode("not valid!@#")