interface GigabitEthernet6/10
 description TRUNK-KBV-SW001
 switchport trunk encapsulation dot1q
 switchport trunk allowed vlan 1,30,31,45,156-158
 switchport mode trunk
 switchport nonegotiate
!
interface GigabitEthernet6/11
 description Offices
 switchport access vlan 31
 spanning-tree portfast
!
interface GigabitEthernet6/12
!
##</code><code>##

#!/usr/bin/perl
my @lines = <>;
my $config = join('', @lines);
my @interfaces = ( $config =~ m/interface.+?\n!\n/gi );
foreach my $interface (@interfaces) {
  print $interface . "\n";
}