As a doctor vs. like a doctor?

[Pressman]

Hello Alan ! Explain please what is proper and why?
He used to work as a doctor.
-
He used to work like a doctor.
thank you

[Alan]

As a doctor means: that was his job - he was employed as a doctor. Like a doctor means: the way in which he worked was the sort of behaviour you would expect from a doctor. It means in the style of/manner of a doctor.
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English as a Second Language
You can read my ESL story A Rhapsody of Words

[Pressman]