This works for the data set provided. It is probably a little less efficient than a solution that breaks the problem into smaller chunks. But it is possible to do it all with one ugly regex. In this case it becomes easier to use named captures than to try to count $1, $2, etc. And the /x option helps to make it more readable.

use strict;
use warnings;

my $string = <<HERE;
MAC Address: xx:aa:aa:aa:aa:aa
  IP addr: a.b.c.d
           x.y.z.f
  Name:  xxxx
  Neighbors attached: 1
    Additional: xxx Interface: xxx Index: xxx
       Link Cost: xx 
       Link Speed: xx Mbps
MAC Address: xx:aa:aa:aa:aa:aa
  IP addr: a.b.c.d
           x.y.z.f
  Name:  xxxx
  Neighbors attached: 1
    Additional: xxx Interface: xxx Index: xxx
       Link Cost: xx 
       Link Speed: xx Mbps
HERE

while( 
    $string =~ m/
        MAC\sAddress:\s(?<mac>\S+)\s+
        IP\saddr:\s(?<ip1>\S+)\s+(?<ip2>\S+)
        .+?
        Link\sCost:\s(?<cost>\S+)\s+
        Link\sSpeed:\s(?<speed>\S+)\sMbps
    /sxg
) {
    print "Node with MAC address: $+{mac} has IP = $+{ip1}, $+{ip2} " 
+.
          "and Link Speed = $+{speed} and Link Cost = $+{cost}\n";
}

[download]

...the output...

Node with MAC address: xx:aa:aa:aa:aa:aa has IP = a.b.c.d, x.y.z.f and
+ Link Speed = xx and Link Cost = xx
Node with MAC address: xx:aa:aa:aa:aa:aa has IP = a.b.c.d, x.y.z.f and
+ Link Speed = xx and Link Cost = xx

[download]

Dave

In reply to Re: regex multiple lines by davido
in thread regex multiple lines by dlal66

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