my $str = 'A2ABA45';
my @parts = $str =~ /A[^A]*/g;

##</code><code>##

my @parts = split /(?=A)/, $str;

##</code><code>##

use Data::Dumper;
my @parts = split /(A.+?)(?=A|$)/, "A2ABA45";
print Dumper(\@parts);

##</code><code>##

my @parts = split /(-)/, "-1-2-";
print Dumper(\@parts);