There are a couple of things that can be improved with your code. I will not address all of them ...

• Instead of the goto you want subroutines (perlsub).
• Don't use global variables if they can be avoided.
• Comparisons like $foo eq ('baz' || 'bar') don't work, use $foo eq 'baz' || $foo eq 'bar' instead.
• Please consider indenting your code properly, e.g. like perltidy does it.
• use warnings; can help you uncover bugs in your code.

To get a bit more concrete, here are some bits and pieces of your code rewritten:

open TESTCASE, "imp2.txt" or die $!;
chomp(@array = <TESTCASE>);

open CONFIGFILE, "imp1.txt" or die $!;
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and instead of the goto OUTER (a similar improvement can be made for goto INNER):

if (...)
{
  $incr++;
  sendMessage();
}

# ...

{
my $msg = <<END;
REGISTER sip: 36.212.176.07 SIP/2.0\r
Via: SIP/2.0/UDP 36.212.176.90:5060; branch= z9hg4bk340\r
...
END

  sub sendMessage
  {
    print "\nSending message:$msg";
    $MySocket->send($msg);
  }
}
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