use strict;
use warnings;

my @x = ("aaBxyz", "..Bxys", "bbxyzzy", "xxAx");

my @result = map { /^..(A|B)./ ? [ $1, $_ ] : () } @x;

# @result is a "2-d array", references to "rows of array"
# I swapped $1 and $_ because I thought the print out looked better

# Of course every map{} can be expressed as a for loop...

foreach my $row_ref (@result)
{
   print "@$row_ref\n";
}

=PRINTS:
B aaBxyz
B ..Bxys
A xxAx
=cut