sub pow{ exp( log( $_[0] ) * $_[1] ) };;

printf "%2d : %20.17f\n", $_, pow( 10**$_, 1/$_ ) for 1 .. 20;;
 1 : 10.00000000000000200
 2 : 10.00000000000000200
 3 :  9.99999999999999820
 4 : 10.00000000000000200
 5 : 10.00000000000000200
 6 :  9.99999999999999820
 7 :  9.99999999999999820
 8 : 10.00000000000000200
 9 :  9.99999999999999820
10 : 10.00000000000000200
11 : 10.00000000000000200
12 :  9.99999999999999820
13 : 10.00000000000000200
14 :  9.99999999999999820
15 :  9.99999999999999820
16 : 10.00000000000000200
17 : 10.00000000000000200
18 :  9.99999999999999820
19 : 10.00000000000000200
20 : 10.00000000000000200

printf "%2d : %20.17f\n", $_, pow( 12345**$_, 1/$_ ) for 1 .. 20;;
 1 : 12345.00000000000500000
 2 : 12345.00000000000500000
 3 : 12345.00000000000500000
 4 : 12345.00000000000500000
 5 : 12345.00000000000500000
 6 : 12345.00000000000500000
 7 : 12345.00000000000500000
 8 : 12345.00000000000500000
 9 : 12345.00000000000500000
10 : 12345.00000000000500000
11 : 12345.00000000000500000
12 : 12345.00000000000500000
13 : 12345.00000000000500000
14 : 12345.00000000000500000
15 : 12344.99999999998400000
16 : 12345.00000000000500000
17 : 12344.99999999998400000
18 : 12345.00000000000500000
19 : 12344.99999999998400000
20 : 12345.00000000000500000