Actually, I use push to put items in a hash all the time. Of course, it's because I want a HoA so I can detect and deal with duplicates. One of the places I use this I then go through the HoA at the end, verify that all arrays have a single member, and then convert from HoA to straight H. I suppose I could do something like this:

  @h{keys %h} = map { $_->[0] } values %h;
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but I think I do this in a slightly longer piece of code.

In another location, I keep the arrays - I need to keep duplicate entries. Think of an XML file - each element can have multiple subelements. In my case, order between elements of different names doesn't matter, so I can put each name into a hash, and have an array of elements that all have that name as a child of the current element. (Does that even make sense?)

So, yes, I use push to populate hashes. It's not the usual way, but it's not uncommon.

(All actual examples of how I do it are removed so as not to give the OP any silly ideas to cut&paste...)