Simple Dice Roller, a la D&D

Invoke-DiceRoll.ps1

function Invoke-DiceRoll {
    [Alias('idr','roll')]
    [CmdletBinding()]
    param(
        [ValidatePattern(
            '^(?:[1-9]|0[1-9]|1[0-9]|20)d(4|6|8|12|20|30|100)$',
            ErrorMessage='Valid die types are d4,d6,d8,d10,d12,d20,d30,d100 rolled beteen 1 and 20 times. Your input was {0}. Please try again.'
        )]
        [string]$Roll = '2d6',
        [switch]$Total
    )
    [int]$Rolls,[int]$Sides = $Roll.Split('d')
    $DiceRolls = for ($i = 1 ; $i -le $Rolls; $i++) {
        Get-Random -Minimum 1 -Maximum ($Sides + 1)
    }    
    if ($PSBoundParameters.ContainsKey('Total') -and $Rolls -ne 1) {        
        ($DiceRolls | Measure-Object -Sum).Sum
    } else {
        $DiceRolls
    }
}