$Path = "$Home\Documents\WindowsPowerShell\tmp"
$ExcludeFiles = '*.psm1'
$IncludeFiles = '*.ps1'

#Bad way!
If($ExcludeFiles)
{
    if($IncludeFiles)
    {
        $Files = Get-ChildItem -Path $Path -Recurse -Include $IncludeFiles
    }
    else
    {
        $Files = Get-ChildItem -Path $Path -Recurse
    }
}
else
{
    if($IncludeFiles)
    {
        $Files = Get-ChildItem -Path $Path -Recurse -Exclude $ExcludeFiles  -Include $IncludeFiles
    }
    else
    {
        $Files = Get-ChildItem -Path $Path -Recurse -Exclude $ExcludeFiles
    }
}