Your SQL looks fine (although I think the words SELECT, FROM, and WHERE should be capitalized). The problem is that you need to execute the SQL statement, then assign the returned information to a data structure.

The code below will push the data that gets returned into a hash for each row, which you can then use to get a number. In this case, it looks like you would only have one row returned but the code below allows for multiple instances of the value.

my @rows;
die qq(SQL failed: ), $db->Error(), qq(\n) if ($db->Sql("SELECT srv_id
+ FROM server_tbl WHERE srv_name='$srv'"));

while ($db->FetchRow()) {
     my %data = $db->DataHash();
     print qq(Index key is $data{"srv_id"}\n); #srv_id value
     # If you want to store information from multiple rows
     push @rows, {%data}; 
}
[download]

You should also check to make sure that your first SQL statement happened correctly. Check out Web Deployment Schemes for some examples on how to work with Win32::ODBC.