if ( $_.PSPath -match ("(?<=::).*?(?=\)")) {
    $user = $matches.Values
}

^

^

^

^[^\rn]*\[^\rn]*\([^\rn]+)

$user = $matches[1]

(?<=^[^\rn]*\[^\rn]*\)[^\rn]+

(?<=\)[^\]*(?=\[A-Z0-9]{40}$)

[^\]*(?=\[A-Z0-9]{40}$)

[^\]*(?=\[A-F0-9]{40}$)

[^\]*(?=\[A-F0-9]*$)