sub fit_data {
    our @ydata;
    local *ydata = shift;
    print "array contains: ",join(",",@ydata)," \n";
    print "last index is $#ydata \n";
};;

fit_data( [ 1..10 ] );;
array contains:  1,2,3,4,5,6,7,8,9,10

last index is 9