If I understand everything correctly then I don't think this is a fourth variant: 
 \@$choices

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compared to 
 $choices

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I think you need to look up array refs and pay particular attention to referencing and dereferencing. In both cases you have an array ref, however in the first you deref it only to then make it a reference again. The second doesn't do this unneccessary merry go round.

HTH.

In reply to Re^3: Passing arrays and references to arrays by simon.proctor
in thread Passing arrays and references to arrays by GrandFather

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