https://www.reddit.com/r/PowerShellChallenge/comments/3ywz6a/challenge_january_2016/

PoShChallenge-201601.ps1

function Invoke-PowerCSV {
    [CmdletBinding()]
    param (
        # Position 1 is implied here, and doesn't need to be specified
		[Parameter(Mandatory = $true)]
        [string[]]$ComputerName,

		[Parameter(Mandatory = $true,
                   ValueFromPipeline = $true)]
        $InputFile,

        # Mandatory = $false is the default
        [int]$UpdateValue
    )

    BEGIN {
        $CSV = Import-Csv -Path $InputFile
    }

    PROCESS {
        If (-not $UpdateValue) { ### This is the Part 1 block
            # Use -contains for array matching, because I'm allowing more than one computer name to be defined
            $CSV | Where {$ComputerName -contains $_.ComputerName} | Select * -ExcludeProperty ComputerName | ForEach-Object {
                # Dynamically discover value columns; no need to assume there will always be five
                ForEach ($Property in ($_ | Get-Member | Where MemberType -eq NoteProperty | Select -ExpandProperty Name)) {
                    Write-Output $_.$Property
                }
            }
        } Else { ### This is the Part 2 block
            # I think the challenge is asking me to:
                # Match ComputerName
                # Remove the value in first position
                # Add UpdateValue in last position
            # Dynamically discover value columns; no need to assume there will always be five
            $Values = $CSV | Get-Member | Where MemberType -eq NoteProperty | Select -ExpandProperty Name | Where {$_ -ne 'ComputerName'}
            # Defining empty array allows for appending objects/rows below (the +=)
            $OverwriteCSV = @()
            ForEach ($CSVRow in $CSV) {
                If ($ComputerName -contains $CSVRow.ComputerName) {
                    # Loop through the row, value by value, moving them forward one column
                    For ($i=0; $i -lt ($Values.Count -1); $i++) {
                        $CSVRow.($Values[$i]) = $CSVRow.($Values[$i+1])
                    }
                    # That loop ignores the last row, so change the last row here
                    $CSVRow.($Values | Select -Last 1) = $UpdateValue
                    # With those value changes made, now the row can be appended
                    $OverwriteCSV += $CSVRow
                } Else {
                    $OverwriteCSV += $CSVRow
                }
            }
            $OverwriteCSV | Export-Csv -Path $InputFile -NoTypeInformation -Force
        }
    }
}