C:\user\perlmonks>perl 11153747.pl 15
32768
0.0403292179107666
0.0388741493225098
v5.38.0

C:\user\perlmonks>perl 11153747.pl 16
65536
0.0916790962219238
0.0764880180358887
v5.38.0

C:\user\perlmonks>perl 11153747.pl 17
131072
0.361366987228394
0.142138957977295
v5.38.0

C:\user\perlmonks>perl 11153747.pl 18
262144
1.22035908699036
0.37365198135376
v5.38.0

C:\user\perlmonks>perl 11153747.pl 19
524288
4.05149698257446
0.628846883773804
v5.38.0

C:\user\perlmonks>perl 11153747.pl 20
1048576
21.3440728187561
3.00999999046326
v5.38.0


##</code><code>##

use strict;
use warnings;
use feature 'say';
use Time::HiRes 'time';

my $n = 2**$ARGV[0];
say $n;
my $x = 'a' x ($n-1);
my $y = 'b' . $x;

my $t = time;
$x =~ s/./$&-/g;
say time - $t;

$t = time;
$y =~ s/./$&-/g;
say time - $t;

say $^V;

__END__