#--- powers
$ib=10;
$x2 = 10.**($ib/2);
print "$x2\n";
$x2 = "1". "0"x($ib/2);
print "$x2\n";

#--- negative power
$ib=3;
$x2 = 10.**(-($ib+1)/2);
print "$x2\n";
$x2 = "0." . "0"x int($ib-1)/2 ."1";
print "$x2\n";