$in = function $in( toMatch, prop ){
        return function( thing ){

            thing = prop ? thing[ prop ] : thing;
            
            var fr = 0
                ,bk
                ;

            if ( Physics.util.isArray( thing ) ){
                bk = thing.length;

                while( fr < bk ){
                    bk--;
                    if (
                        // check front
                        (indexOf(toMatch, thing[ fr ]) > -1) ||
                        // check back
                        (indexOf(toMatch, thing[ bk ]) > -1)
                    ) {
                        return true;
                    }
                    fr++;
                }
                return false;
            }

            // if thing matches any in array
            return (indexOf(toMatch, thing) > -1);
        };
    }
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$in( toMatch[, prop] ) -> Function
- toMatch (Array): The array to match
- prop (String): The property name to test

Get a test function for matching ANY in array