@_ = a..z;
$_ = join '', @_;

/
  .{5}    # 5 symbols neglected
  (.{3})  # next 3 captured
  .{5}    # another 5 missed
  (.{3})  # and again 3 captured
/x;

print "$1 $2 \n"

__END__

STDOUT: fgh nop
where:
1 a 
2 b 
3 c 
4 d 
5 e 
6 f 
7 g 
8 h 
9 i 
10 j 
11 k 
12 l 
13 m 
14 n 
15 o 
16 p 
17 q 
18 r 
19 s 
20 t 
21 u 
22 v 
23 w 
24 x 
25 y 
26 z