using namespace System.Collections.Generic
$list = [List[string]] @('ggg');
'$list={0}' -f ($list -join ', ') | oh
function f {$list.Add('fff'); 'f={0}' -f ($list -join ', ') | oh;}
&{$list.Add('sb'); 'sb={0}' -f ($list -join ', ')|oh;}
f
'$list={0}' -f ($list -join ', ') | oh
↓
$list=ggg
sb=ggg, sb
f=ggg, sb, fff
$list=ggg, sb, fff