Using Conditional Statements in Windows PowerShell 2

As you automate your Windows operating system with PowerShell 2, you use conditional statements to run different script blocks depending on a specific condition, usually using an if/else or switch statement. Following are examples of conditional statements:

$size = "M"
if ($size -eq "S") {
     Write-Host "Small"
} elseif ($size -eq "M") {
     Write-Host "Medium"
} else {
     Write-Host "Large"
}
$size = "M"
switch ($size)
{
   "S"   {Write-Host "Small"}
   "M"   {Write-Host "Medium"}
   default {Write-Host "Large"}
}

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Source:http://www.dummies.com/how-to/content/using-conditional-statements-in-windows-powershell.html