Should this not be an error ?

[Alex Tweedly]

Mark Wieder wrote:
> Alex-
>
> Saturday, May 9, 2009, 8:31:33 AM, you wrote:
>
>   
>> Shouldn't this be a compile error ?
>>     
>
> Same answer as the other question. If tracking this kind of error down
> seems like a pain then turn on explictVars and get in the habit of
> declaring variables.
>   

I accept that for 'chr'  (though I wonder what  "the last myVar of temp" 
means) ?
But for the other example, I don't get it. Why is
>     if the last line of t is empty then delete line -` of t
affected by variable checking ?    Is ` a variable name ?

Oops - just tried it and it  *is* ?  I am amazed :-)
Is there anywhere defined the set of characters that can be used in a 
variable name ?

-- Alex.