Strictly speaking, you should respect the following distinctions:
Like is a preposition. It is followed by a noun, a pronoun or a gerund, for example
You look like your sister/ She looks like you/ Having a dog is a bit like having a small child
As is a conjunction. It is followed by a clause with a subject and verb, for example
We've adopted a dog, as I told you.
As is also used before prepositional expressions, for example:
In South Africa, they drive on the left-hand side of the road, as in Europe.
However, more and more, people are using like instead of as, for example
We've adopted a dog, like I told you
...they drive on the left-hand side of the road, like in Europe.
But this is still considered incorrect in formal English.
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