use strict;
my $mystring = "AABAABAA";
my @array;
{} while $mystring =~ /A(?=ABAA)(?{push @array, pos($mystring)})/g;
print join(",", @array),"\n";

#or without any fancy "experimental" regex stuff

@array=();
while ($mystring =~ /A(?=ABAA)/g) {
	push @array, pos($mystring)
}
print join(",", @array),"\n";

__OUTPUTS__

1,4
1,4