use strict;
use warnings 'all';

my $str = do {local $/ = undef; <DATA>};
my @Rec = $str =~ /-+\s+show switchname\s+-+[^\w]+(\w+)/ig;

print "$_\n" for @Rec;

##</code><code>##

__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
******************************************************************

##</code><code>##

CCC217_ANG_GREEN
CCC218_ANG_GREEN
CCC219_ANG_GREEN
CCC220_ANG_GREEN