[Mesorah] az + imperfect

[Sholom Simon via Mesorah]

So now I'm hopeless confused.  Re: Az Yashir you wrote:

 > Yes, it was a normal construction.  Not only used with "az," but 
also with "terem."  They are always followed by a verb in the 
imperfect (AKA future) tense, whether or not they refer to past or 
future tense.

So, are the usages in  4:26 & 4:10 idioms?  Exceptions?  If 
exceptions, is there a rule they follow?  (It certainly doesn't seem 
out of the ordinary: 4:26 has "az amara..."  ("then she said"))

At 11:34 AM 1/1/2016, Mandel, Seth wrote:
>The fact that there is a specific morphological form used in a 
>specific syntactical usage does not mean that the same morphological 
>form can be used elsewhere with a different meaning.
>Similarly in idioms. Pins and needles has a specific meaning 
>involving neither pins nor needles. But both words cash be used 
>outside that phrase in different meanings.
>Languages are all very tricky and slippery beasties, reflecting the 
>human mind. There is no such thing known as a "primitive language" 
>that is not tricky and slippery.
>
>Rabbi Seth Mandel
>Sent from my iPhone
>
> > On Jan 1, 2016, at 11:18 AM, "Sholom Simon via Mesorah" 
> <mesorah at lists.aishdas.org> wrote:
> >
> > Recently I was discussing with some folks on this list (or what 
> it _on_ this list?  My memory ain't what it used to be) about the 
> phrase "Az yashir", and somebody pointed me to an on-line 
> grammar/diduk translation that pointed out that "Az" and "terem" 
> are followed by the imperfect tense.
> >
> > But there are a number of times in this parsha (e.g., 4:26, 4:10) 
> when "az" is not followed by the imperfect.
> >
> > Thoughts?
> >
> > -- Sholom