The building a hash was just an example, not the point of the function. For the function in general, no error checking is possible because there are no error conditions. Every input has a well-defined output. For instance, interleave() returns an empty list, interleave('a'..'e') returns ('a','d','b','e','c').

Given actual arrays, I would be more likely to say:

%h = ();
@h{@keys} = @values;
[download]