$VerbosePreference = "Continue"

#check if valid email address
$str = "[email protected]"
$pattern = "^[A-Z0-9._%+-]+@[A-Z0-9.-]+\.(?:[A-Z]{2}|com|org|net|gov|ca|mil|biz|info|mobi|name|aero|jobs|museum)$"

if ($str -match $pattern)
{
   Write-Verbose "Valid Email Address"
}
else
{ 
  Write-Verbose "Invalid Email Address"
}

#another way to test 
[Regex]::Match($str, $pattern)

#can also use regex in switch
$str = "V1A 2V1"
$str = "90250"

switch -regex ($str)
{
   "(^\d{5}$)|(^\d{5}-\d{4}$)" 
   { 
        Write-Verbose "Valid US Postal Code" 
   }
   "[A-Za-z]\d[A-Za-z]\s*\d[A-Za-z]\d"
   {
        Write-Verbose "Valid Canadian Postal Code" 
   }
   default 
   { 
        Write-Verbose "Don't Know" 
   }
}

#use regex and extract matches...