use warnings;
use strict;
use Data::Dumper;

my @CELLS=( 'A-1', 'A-2', 'A-3', 'A-4', 'B-5', 'B-6', 'C-7', 'C-8');

my %hash;
for (@CELLS) {
    /^(.*)-(\d+)$/ and push @{ $hash{$1} }, $2
}
print STDERR "hash DUMPER:\n", Dumper(\%hash), "\n";