that wasn't supposed to happen-

I hope Frolik does too

both did

If anyone would have wanted him they would have signed him

That's not how it works

When he signed for near league minimum 2 weeks before the season it is

It makes no difference when the contract was signed. It's a two-way street.

In short, here's the chronology of things.
A) Player offers his services to the league at NHL minimum.
B) Agent gets no offers
C) Player picks the team where he wants to be on their taxi squad (Perry and Frolik both choose the Habs).
D) Team (Habs) sign him and put him on waivers.
E) Rest of the league, if they regretted not signing him before, has one last chance to change their mind, but it's only for their regular roster, not their taxi squad.
F) After a day on waivers, no one picks him up because "see point B."

Any team who would pick him up would have to keep him on their 20-23 man roster, so he would count against their cap.

But now, because no one did, the Habs have him and he doesn't even count against the cap. Even when he plays he'll just be replacing someone else's salary, so we basically get both him and Frolik for free.

Well played Marc Bergevin. Well played.

Being a two-way street is my point? if teams were interested he would have gotten either more money or signed earlier.

Two way street as in Perry didn't want to sign there. He's already made his money so he's not going anywhere for the money, he's going to go where he thinks it will be the right fit for him.