hehehe

#!/usr/bin/perl -l

# http://perlmonks.org/?node_id=1173445

use strict;
use warnings;

sub hehehe
  {
  @_ < 2 and return @_;
  my ($left, $right) = ( 0, @_ + 1 >> 1 );
  my @halves = ( hehehe(@_[0..$right-1]), hehehe(@_[$right..$#_]) );
  @halves[ map $right > $#_ ||
    $left <= $#_ >> 1 && $halves[$left] <= $halves[$right]
    ? $left++ : $right++, 1 .. @_ ];
  }

print join ', ', my @array = qw(1 4 6 7 23 45 12 1 2);
print join ', ', hehehe @array;
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