I think that GrandFather's regular expression solution is the best for you but you ask what other solutions we have. davido has come up with an improved substr solution. Here's a way with split, splice and join.

use strict;
use warnings;

my $str = q{12345678};
print qq{$str\n};

$str = revByGroup($str);
print qq{$str\n};

sub revByGroup
{
    my $str = shift;
    my @chars = split m{}, $str;
    for (my $idx = 0; $idx < $#chars; $idx += 2)
    {
        splice @chars, $idx, 0, splice @chars, $idx + 1, 1;
    }
    return join q{}, @chars;
}

[download]

and the output is

12345678
21436587

[download]

It copes with an odd numer of characters, leaving the last odd character at the end of the string. I hope this is of interest.

Cheers,

JohnGG

In reply to Re: What is the best solution to swap input data? by johngg
in thread What is the best solution to swap input data? by bh_perl

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.