Understanding GetNewClosure. Assuming you have Pester installed, but not required. Remove Should parts.

GetNewClosure.ps1

# No GetNewClosure - print $a as what ever it is before printing

& {
    $a = 10
    $myScript = {
        $a
    }
    & $myScript
    $a = 20
    & $myScript
} | Should -Be @(10, 20)

# GetNewClosure - print $a as what it was at the time of creation

& {
    $a = 30
    $myScript = {
        $a
    }.GetNewClosure()
    & $myScript
    $a = 40
    & $myScript
} | Should -Be @(30, 30)