Open successive arrays of URLs in IE

1. If $site is the first or only URL in the array, and IE is not open, then the URL opens in the first tab. On the next run, the next array is opened if $search = $true.
2. If $site is the first or only URL in the array, and IE is open, then the URL opens in a new tab. QUESTION: On the next run, why is the same array opened?
3. If $site is not the first or only URL in the array, then the URL opens in a background tab.

function OpenSites($sites) {
    $isFirstSite = $true
    foreach ($site in $sites) {
        if ($isFirstSite -eq $true) {
            if ($newInstance) {
                $ie.Navigate2($site)
            } else {
                $ie.Navigate2($site, $navOpenInNewTab)
            }
        } else {
            $ie.Navigate2($site, $navOpenInBackgroundTab)
        }
        $isFirstSite = $false
    }
}

$today = (get-date).DayOfWeek
switch ($today) { 
    "Someday" {
        $search = $false
        # Check if Google open
        foreach ($tab in $ie) {
            if ($tab.LocationURL.Contains("http://www.google.com/"))
            { $search = $true; break }
        }
        # If Google open on 2nd run, open Yahoo
        if ($search) {
            OpenSites -sites "http://www.yahoo.com/"
        } else {
            # 1st run
            OpenSites -sites "http://www.google.com/ncr","http://www.bing.com/"
        }
    }
}

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