my %line=qw(A 1 B 1 C 1);
my @tojoin = qw (W X Y Z); 

for my $l(sort keys %line){
  for my $k(@tojoin){
    $line{qq($l$k$_)}=1
        for @tojoin
  }
};

print qq($_\n) for sort keys %line ;

-- Output ---
A
AWW
AWX
AWY
...snip...
B
BWW
BWX
...snip...
BZZ
C
CWW
...snip...
CZZ