Looking at my docs (might be outdated) it says, describing AddConnection:

  AddConnection( \%NETRESOURCE, $Password, $UserName, $Connection )
      Makes a connection to a network resource specified by %NETRESOURCE 

so wouldn't you instead _not_ create your $connect_string but rather use the values directly?   You already have the hash reference in $net_resource.

  if( AddConnection($net_resource, $win2k_pwd, $win2k_uid, $Connection
+) ) {
[download]

Man, that's a strange order for the arguments!   And do you need to pre-declare $Connection?   And maybe the desired effect ala "/persistent:no" is simply accomplished through _not_ using Scope => RESOURCE_REMEMBERED, in your hash?   These are some things to try until others can give specific answers.