c:\@Work\Perl\monks>perl -wMstrict -le
"my $s = '.net,.Net; .NET;.net, Visual Basic Visual Basic; VisualBasic
+x Visual Basic,Visual Basic';
 ;;
 for my $kw (qw(.NET C C++), 'Visual Basic') {
   my $count = () = $s =~ m{ (?: (?<! \S) | (?<= [,;])) \Q$kw\E (?: (?
+! \S) | (?= [,;])) }xmsig;
   print qq{'$kw' $count};
   }
"
'.NET' 4
'C' 0
'C++' 0
'Visual Basic' 4
[download]

But that's not to say your basic approach isn't better!