Not too difficult:

my $string = "AAACANANANTANAACATNNCAAAAAA";
my @matches = $string =~ /([AN]+)/g;
$\=$,=$/;
print @matches;
__DATA__
output:
AAA
ANANAN
ANAA
A
NN
AAAAAA
[download]

As for everything else: opendir, readdir, closedir, glob, open, perlopentut, and of course the Schwartzian Transform.

Hope this helps.

antirice    
The first rule of Perl club is - use Perl
The ith rule of Perl club is - follow rule i - 1 for i > 1