Why aren't colons optional?

[Marc Poulin]

In article <u4oc4g84pfuv4d at news.supernews.com>, "John Roth"
<johnroth at ameritech.net> wrote:

>> I've also always found the interchangability of ' and " to be a bit
>> amusing.  Seems like it was just a bone to throw to the "there's more
> than
>> one way to do it" camp.  

Thus spake Niklaus Wirth:

  $string = '"'{character}'"' | "'"{character}"'".
        -- Programming in Modula-2 (3rd ed., 1985), p. 15