#!/usr/bin/perl

use strict;
use warnings;

while (<DATA>) {
    # only check between --- show switchname --- and *****
    if ( /^-+ show switchname -+/ .. /^\*+/ ) {
        # only pick up the word between these two lines
        print "$1\n" if /(^\w+)/;
    }
}

__DATA__
 show tech-support details

-------------------- show switchname ------------------
CCC217_ANG_GREEN
******************************************************************
 show tech-support details

-------------------- show switchname ------------------
CCC218_ANG_GREEN
******************************************************************

 show tech-support details

-------------------- show switchname ------------------
CCC219_ANG_GREEN
******************************************************************
 show tech-support details

-------------------- show switchname ------------------
CCC220_ANG_GREEN
******************************************************************