#!/usr/bin/perl

use strict;
use warnings;
use feature 'say';

my $text='abc 1foo 1x1 ee2 3B4 n 5 6t7 q9q 5+6';
while ($text=~/(\d)([[:alpha:]])(\d)/g) {
        if ($1 + 1 == $3) {
                say "$1$2$3 is wanted because $1 + 1 = $3";
        } else {
                say "$1$2$3 matches, but is not wanted ($1 + 1 != $3)";
        }
}