use strict;
use warnings;

my %port_channels;

{
   my $channel;
   my $in_ports = 0;

   while (<DATA>) {
      if (/^port-channel\s+(\d+)/) {
         $channel = $1;
         $port_channels{$channel} = [];
         $in_ports = 0;
         next;
      }

      next unless defined $channel;

      if (/^\s*Ports:\s+(\S+)\s+\[/) {
         $in_ports = 1;
         push(@{$port_channels{$channel}}, $1);
         next;
      }

      if ($in_ports) {
         if (/\s+(\S+)\s+\[/) {
            push(@{$port_channels{$channel}}, $1);
            next;
         }

         $in_ports = 0;
      }
   }
}

require Data::Dumper;
print(Data::Dumper::Dumper(\%port_channels));

__DATA__
port-channel 1
    Administrative channel mode is on
    Operational channel mode is on
    Last membership update succeeded
    First operational port is fc1/5
    2 ports in total, 2 ports up
    Ports:   fc2/5    [up]  
             fc1/5    [up] *

port-channel 3
    Administrative channel mode is on
    Operational channel mode is on
    Last membership update succeeded
    First operational port is fc1/1
    1 port in total, 1 port up
    Ports:   fc1/1    [up] *