#!/usr/bin/perl -w
use strict;

my ($state, %data);

for (<DATA>){
    $state = $1 if /^(Router|Network|Extern)/;
    push @{$data{$state}}, $_;
}

# Display the saved data
for my $st (sort keys %data){
    print "$st:\n";
    for (@{$data{$st}}){
        print "\t$_";
    }
}

__DATA__
Router
abc
def
ghi jkl
Network
Extern
foo
bar
qux
zotz
Router
blah
Network