Yeah, this is a place you need to pay careful attention to the wording. It has to be a scalar variable, not just a scalar.

Like foo() could return a scalar, and that scalar could be a reference to a filehandle. But print foo() "string\n" will fail because even though foo() evaluates to a scalar, it's not a scalar variable. Nor is $foo{'somekey'}.

Same as you're not allowed to do:

my %foo;
for $foo{'somekey'} ( @arr ) {
  ...;
}
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