& {
     param(
         [string]
         [Parameter(Position=0)]
         $Root,

         [string[]]
         [Parameter(Position=1, ValueFromRemainingArguments)]
         $Extra)
     $Extra.Count;
     for ($i = 0; $i -lt $Extra.Count; $i++)
     {
        "${i}: $($Extra[$i])"
     }
 } root aa,bb

Add-Type -OutputAssembly $env:temp\testBinding.dll -TypeDefinition @'
    using System;
    using System.Management.Automation;

    [Cmdlet("Test", "Binding")]
    public class TestBindingCommand : PSCmdlet
    {
        [Parameter(Position = 0)]
        public string Root { get; set; }

        [Parameter(Position = 1, ValueFromRemainingArguments = true)]
        public string[] Extra { get; set; }

        protected override void ProcessRecord()
        {
            WriteObject(Extra.Length);
            for (int i = 0; i < Extra.Length; i++)
            {
                WriteObject(String.Format("{0}: {1}", i, Extra[i]));
            }
        }
    }
'@

Import-Module $env:temp\testBinding.dll

Test-Binding root aa,bb

> $PSVersionTable
Name                           Value
----                           -----
PSEdition                      Core
PSVersion                      6.0.0-alpha
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0...}
WSManStackVersion              3.0
GitCommitId                    v6.0.0-alpha.9-107-g203ace04c09dbbc1ac00d6b497849cb69cc919fb-dirty
PSRemotingProtocolVersion      2.3
CLRVersion
SerializationVersion           1.1.0.1
BuildVersion                   3.0.0.0