Needs Perl version 5.10+ for  \K operator:

c:\@Work\Perl\monks>perl -wMstrict -le
"use 5.010;
 ;;
 for my $s (
   '2       INT_NET       Net   : c_c',
   '2       INT_NET       Net   : b_c',
   '2       INT_NET       Net   : a_c',
   ) {
   printf qq{'$s' -> };
   my ($net_name) = $s =~ m{ : \s* \K \w+ }xmsg;
   print qq{'$net_name'};
   }
"
'2       INT_NET       Net   : c_c' -> 'c_c'
'2       INT_NET       Net   : b_c' -> 'b_c'
'2       INT_NET       Net   : a_c' -> 'a_c'
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