When in trouble with perlop precedence always use parentheses.

The 1. variant

> return something() or croak "something didn't work";

equals

(
   ( return something() ) 
   or 
   ( croak "something didn't work" )
);
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But doesn't make much sense, because the or-branch is never reached.

A "normal" return almost never fails, and if return fails, the program dies right away:

> perl
return
__END__
Can't return outside a subroutine at - line 2.
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(update: one might argue that the former shouldn't even compile, but there are probably use-cases in combination with do FILE )

The 2. variant

> return something() || croak "something didn't work";

equals

 
return ( 
    ( something() ) 
    or 
    ( croak "something didn't work" )
);
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which looks a bit strange but is somehow possible.

still Carp::croak() means to die

    # die of errors (from perspective of caller)
    croak "We're outta here!";
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so returning the value of croak doesn't really make sense either.

update

The latter means mixing two very different control flows in one line ... irk.

In the spirit of PBP : "make control flows immediately clear!", mixing two is quite confusing for the reader.