use strict;
use warnings;

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

# for each element in the array @x, 
# pass that element to the array @result if
# if the 3rd character is either A or B
# followed by at least one character.

my @result = grep {/^..(A|B)./}@x;

print "$_\n" for @result;

=prints
aaBxyz
..Bxys
xxAx
=cut

##</code><code>##

#ok, with a weird example of $1
@result = grep{ print "$1 $_\n" if /^..(A|B)./;
                /^..(A|B)./}@x;
                
=prints
B aaBxyz
B ..Bxys
A xxAx
=cut
@result is the same as above

# grep {} executes the code within the brackets and passes the input
# to @result depending upon the true/false value of the last statement.