I need to convert a Perl script to VB.NET. I have managed almost the entire conversion, but some Perl (seemingly simple) regex are causing an headache. Can someone suggest me .NET equivalent of the following perl regex:

1)

$letter =~ s/Users //,;
$letter =~ s/Mailboxes //,;
if($letter =~ m/$first_char/i){

2)

unless($storegroup =~ /Recovery/ || $storegroup =~ /Users U V W X Y Z/ || $storegroup =~ /Users S T/
    || $storegroup =~ /Users Q R/){

The regex look simple to me. I tried to wade through perl.org but understanding a langugae regex takes sometime and I need to complete the conversion quickly.