What do you do when the pattern you search for is at a boundary, taking either increment or decrement out of range? In your example above, you match near 'AAA30'. Do you only look for 'AAA30' and 'AAA31'? Do you also look for 'AAA29'?
If so, the hash-key idea won't work, because you're not only changing the last character.
You could do something like this for each of pattern:
my ($pat, $char) = $pattern =~ m/(.*)(.)$/;
my $char_up = $char;
my $char_down = $char;
++$char_up unless ($char =~ m/[9Z]/i);
--$char_down unless ($char =~ m/[0A]/i);
my $search = qr/$pat$char|$pat$char_up|$pat$char_down/;
print $search;
How many patterns do you have anyway? How many lines do you search?