https://blog.netwrix.com/2018/10/04/powershell-variables-and-arrays/

$var_str1 = "Hello";
$var_str2 = "World";
$var_str3 = $var_str1 + $var_str2
$var_str3  # HelloWorld

$var_int1 = 10;
$var_int2 = 20;
$var_int3 = $var_int1 + $var_int2
$var_int3  # 30

$var_type_conv = $var_str1 + $var_int1
$var_type_conv  # Hello10

$str_to_int = [int]"123"

$var_array = "apple", "orange", 123
$var_array.GetType().FullName # 属性和命令均不区分大小写
$var_array2 = @(elem1, elem2)

$var_hashtable = @{
    "key1" = "value1"; # 能用分号或者直接留空，但不能加逗号
    "key2" = 123
}

# 作用域
# Global: 在当前powershell交互环境（会话）里一直有效
# Script: 整个psl脚本
# Local: 当前作用域（块）

$global:var
$script:var
$local:var

# 清空变量，或置空
Clear-Variable -Name var_str1 # 现在var_str1值为$null

# 销毁变量
Remove-Variable $var_str1 # 现在var_str1变量不复存在，访问会报错

Set-Variable -Name "myVariable" -Description "This is my sample variable"