Hi Sinhaa -
You've discovered the key difference between the Perl API bindings in the NMSDK and the PowerShell toolkit. The NMSDK, and with the Perl bindings in particular, easily exposes the entire SDK from basic connection methods, the lowlevel XML building mechanisms, and a single function wrapper around each individual ZAPI function call that handles both the XML building from and recoveyr into convenient Perl data structures. The entire API is accessible including higher privilege level options and commands.
The PowerShell toolkit is much more a convenience wrapper around common functions for those in a Windows environment. It doesn't expose the entire API, it doesn't expose all the parameters of the APIs that it does wrap (for instance, you can't access or use options only available in Advanced or Diagnostic mode), and security is somewhat Windows centric in that it uses a saved credential model similar to other Windows systems.
As my company tends to be more Windows centric the PowerShell toolkit tends to be the default utility used for most automation, but I drop to the Perl NMSDK bindings for almost everything I do of substance because I need the abilities it provides. I've asked through many channels for the PowerShell toolkit to at least add Advanced mode privilige options for a number of the cmdlets it provides. Haven't yet seen any indication that those will be forthcoming.