If the original problem is:

Say I want to select specific items from this list, say, "down", "out" and "left". This might be represented by another array:

@arr = qw ( up down in out left right );  # 6 elements
@sel = ( 1, 3, 4 );
@my_items = Magic(@arr, @sel);
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Then the following, Perl built-in solution does what you want already:

@my_items = @arr[ @sel ];
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I'm not sure if you want to pursue your bit-field path further...