------- Sample Text ------- 
!
interface Ethernet
 blah...
 blah...
!
interface Gigabit
 blah...
 blah...
!
interface Ethernet
 blah...
!
------- Sample Text ------- 

##</code><code>##

foreach $line (@cfg) {
   if ($line =~ m/^interface (\.*)/) { 
      if ($1 eq "Ethernet") {
         &parse_ethernet($1);
         Keep parsing until $line matches "!"
      }
      if ($1 eq "Gigabit") {
         &parse_gigabit($1);
         Keep parsing until $line matches "!"
      }
   }
   if ($line =~ m/^system (\.*)/) { 
       blah...
   }
}