in reply to Perl Idioms Explained - ${\$obj->method} and @{[sort @list]}

One must be careful with the ${\foo} because if foo returns something that isn't a simple scalar value then you might get unexpected results.

To be more precise, the \ operator gives its argument list context, which may surprise many people (it did me). The other interpolation construct @{[  ]} also provides list context. This is something to be aware of, and use of scalar will be appropriate in some cases, including in ${\scalar foo}.