A slick way to do overloads in powershell.

Get-FullName.ps1

function Get-FullName {
    param(
        [parameter(position=0, parametersetname="a")] [string] $firstName,
        [parameter(position=1, parametersetname="a")] [string] $lastName,
        [parameter(position=0, parametersetname="b")] [hashtable] $name
    )

    if($PSCmdlet.ParameterSetName -eq 'b') {
        # Doing recursion will allow for parameter validation if need be!
        Get-FullName $name.first $name.last
        return
    }

    "{0} {1}" -f $firstName, $lastName
}

Get-FullName "john" "doe"
Get-FullName  @{'first'='bob'; 'last'='smith'}