Get-PossibleWordCombinations

function Get-PossibleWordCombinations {
    [cmdletbinding()]
    param(
        [parameter(Mandatory=$true)]
        [String]$Word,
        [parameter(Mandatory=$true)]
        [hashtable]$Map,
        [switch]$NoCaseConsideration
    )
    $list = New-Object System.Collections.ArrayList
    $queue = New-Object System.Collections.Queue
    [void]$list.Add($word)
    $queue.Enqueue($word)
    while($queue.Count -gt 0){
        $o = $queue.Dequeue()
        for($i = 0 ; $i -lt $o.Length;$i++){
            foreach($key in $map.Keys) {
                if($o[$i] -ieq $key) {
                    foreach($val in $map[$key]) {
                        $newO = $o.Remove($i,1).Insert($i,$val)
                        if( -not $list.Contains($newO)){
                            [void]$list.Add($newO)
                        }
                        $queue.Enqueue($newO)
                    }
                }
            }
        }
    }
    if($NoCaseConsideration) {
        $list
    } else {
        .{
            foreach($combo in $list) {
                for($i=0;$i -lt [math]::Pow(2,$combo.length);$i++){
                    $res=@()
                    for($j=0;$j -lt $combo.length;$j++) {
                        if([bool]($i -band [math]::Pow(2,$j))){
                            $res+=([string]$combo[$j]).ToUpper()
                        } else {
                            $res+=([string]$combo[$j]).ToLower()
                        }
                    }
                    -join $res
                }
            }
        } | Sort-Object -Unique -CaseSensitive
    }
}

# Example:
$passwords = Get-PossibleWordCombinations -Word "password" -Map @{a="@","4";o="0"}
$passwords.Count