"and then" / "or else"

Hi list,
the logical operators "and" and "or" are commutative, i.e. there is no
"short-circuiting". Especially when doing PL/pgSQL development it would
sometimes be very handy to have this short circuiting. Unfortunately,
the trick from the docs (chapter 4.2.12) using "case ... then" does not
work inside an "if" statement (the "then" of the "case" is interpreted
as belonging to the "if" and thus leads to a syntax error).
Of course, I can sometimes use nested "if" statements, but that doesn't
always meet the logical requirements and leads to less readable code.
Some programming languages (e.g. Eiffel) know the operators "and then"
and "or else" which explicitly are "short-circuited". Would it be
possible to add these operators to PostgreSQL in general or at least to
the PL/pgSQL syntax?

Regards,
    Christian

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