use strict;
my $str = 'interface GigabitEthernet1/12
description ** Unused Port **
switchport access vlan 1002
switchport mode access
switchport port-security
switchport port-security mac-address sticky
shutdown
no cdp enable
spanning-tree portfast
!
interface GigabitEthernet1/13
description ** Unused Port **
switchport access vlan 1002
switchport mode access
switchport port-security
switchport port-security mac-address sticky
shutdown
no cdp enable
spanning-tree portfast
!
';
my $regex = qr/interface GigabitEthernet1\/(1[2-9]|[1-2][0-1]).*\n(.*\n)*.* description \*\* Unused Port \*\*.*\n(.*\n)*.* switchport access vlan 1002.*\n(.*\n)*.* switchport mode access.*\n(.*\n)*.* switchport port-security.*\n(.*\n)*.* switchport port-security mac-address sticky.*\n(.*\n)*.* shutdown.*\n(.*\n)*.* no cdp enable.*\n(.*\n)*.* spanning-tree portfast
/p;
my $subst = '';
my $result = $str =~ s/$regex/$subst/r;
print "The result of the substitution is' $result\n";
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Perl, please visit: http://perldoc.perl.org/perlre.html