Mastering Windows PowerShell Scripting - Third Edition

Expressions

Switch allows expressions (a ScriptBlock) to be used in place of a simpler condition. The result of the expression should be an explicit true or false, or an implicit Boolean, for example:

switch (Get-Date) {    { $_ -is [DateTime] } { Write-Host 'This is a DateTime type' } 
    { $_.Year -ge 2017 }  { Write-Host 'It is 2017 or later' } 
}