Get-LinkFieldUrl.ps1

function Get-LinkFieldUrl {
    [CmdletBinding()]
    param(
        [Parameter(Position = 0, Mandatory = $true, ValueFromPipeline = $true)]
        [ValidateNotNullOrEmpty()]
        [Sitecore.Data.Items.Item]$Item        
    )
    # Regular expression to extract the URL
    $regex = '<link\s+url="([^"]+)"'

    $linkFieldValue = $Item.Fields["My Link Field"].Value;
    if ($linkFieldValue -ne "") {
        if ($linkFieldValue -match $regex) {
            $urlValue = $matches[1]
            return $urlValue
        } 
    }
}