How to get the value of the PATH environment variable without expanding tokens?

This isn't PowerShell per se, but a "feature" of the underlying Windows registry. The Path variable is of type REG_EXPAND_SZ which automatically expands environment variables on retrieval. I don't think you can get around it with the built-in cmdlets, but you can with the .NET Microsoft.Win32.Registry APIs. Use the RegistryKey.GetValue overload with RegistryValueOptions.DoNotExpandEnvironmentNames:

$regKey = [Microsoft.Win32.Registry]::LocalMachine.OpenSubKey('SYSTEM\CurrentControlSet\Control\Session Manager\Environment', $true)$regKey.GetValue('Path', $null, "DoNotExpandEnvironmentNames")

when it is time to save the variable, use the overload of SetValue with RegistryValueKind.ExpandString to save it with the correct type:

$regKey.SetValue("Path", $new_path, "ExpandString")

Without using the .NET [Microsoft.Win32.Registry] type: one-liners for user and system Path entries.

(Get-Item -path "HKCU:\Environment" ).GetValue('Path', '', 'DoNotExpandEnvironmentNames')(Get-Item -Path "HKLM:\SYSTEM\CurrentControlSet\Control\Session Manager\Environment" ).  GetValue('Path', '', 'DoNotExpandEnvironmentNames')