use strict;
use warnings;

use 5.010;

use Benchmark qw(:all :hireswallclock) ;

my $inputA = "X".(" \t" x 200000)."A";
my $inputB = "X".(" \t" x 200000)."B";

my $c1A = <<'CODE';
my $s = $inputA;
$s =~ s/[\s\u200c]+A/ A/;
CODE

my $c1B = <<'CODE';
my $s = $inputB;
$s =~ s/[\s\u200c]+A/ A/;
CODE

my $c2A = <<'CODE';
my $s = $inputA;
$s =~ s/(?<=\S)[\s\u200c]+A/ A/;
CODE

my $c2B = <<'CODE';
my $s = $inputB;
$s =~ s/(?<=\S)[\s\u200c]+A/ A/;
CODE

timethis(50_000_000,$c1A);
timethis(50_000_000,$c1B);
timethis(50_000_000,$c2A);
timethis(50_000_000,$c2B);