Expanding the solution to allow for reversing groups of multiple elements.

use strict;
use warnings;

use feature qw{ say };
use List::Util qw{ min };

my @arr = ( 1 .. 9 );
say qq{@arr};

my @twos = reverseGroupsOf( 2, @arr );
say qq{@twos};

my @threes = reverseGroupsOf( 3, @arr );
say qq{@threes};

my @fours = reverseGroupsOf( 4, @arr );
say qq{@fours};

sub reverseGroupsOf
{
    my $groupsOf = shift;
    my $rcReverse;
    $rcReverse = sub
       {
           reverse( map shift, 1 .. min scalar( @_, $groupsOf ),
           @_ ? &$rcReverse : ();
       };
    &$rcReverse;
}

[download]
1 2 3 4 5 6 7 8 9
2 1 4 3 6 5 8 7 9
3 2 1 6 5 4 9 8 7
4 3 2 1 8 7 6 5 9

[download]

I hope this is of interest.

Cheers,

JohnGG

In reply to Re^3: Switch the odd/even elements of an array by johngg
in thread Switch the odd/even elements of an array by jaredor

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