#  Designed for a specific implementation
function Validate-Expression
    {
    Param (
        [string]$Expression )

    #  Expected token types (plus 'Member' handled separately)
    $SafeTokenTypes = @(
        'String'
        'Variable'
        'Type'
        'Operator'
        'GroupStart'
        'GroupEnd'
        'NewLine')

    try
        {
        #  Use PowerShell parser to tokenize expression
        $Tokens = [System.Management.Automation.PSParser]::Tokenize( $File, [ref]$Null )
        }
    catch
        {
        #  Expression cannot be parsed
        #  Return unsafe
        return $False
        }

    #  If successfully found tokens...
    #  (Else null expression; return nothing)
    If ( $Tokens )
        {
        #  For each token
        #  (Using index so we can reference next token
        ForEach ( $Index in 0..($Tokens.Count-2) )
            {
            #  If token is not something safe
            #  or is not a Member followed by an Operator
            #  ( "Property =" is safe. "Method(" is not )
            If (      $Tokens[$Index].Type -notin $SafeTokenTypes -and
                    ( $Tokens[$Index].Type -ne 'Member' -or
                      $Tokens[$Index+1].Type -ne 'Operator' ) )
                {
                #  Return Unsafe
                return $False
                }
            }
        #  Check last token
        #  If token is not something safe
        If ( $Tokens[-1].Type -notin $SafeTokenTypes )
            {
            #  Return unsafe
            return $False
            }

        #  All tests passed
        #  Return safe
        return $True
        }
    }

function Import-WeirdFile
    {
    Param (
        [string]$Path )

    #  Get the first and second "Something =" strings
    $ParentArray, $ArrayItem = Get-Content -Path $Path |
        Where-Object { $_ } |
        Select-Object -First 2 |
        ForEach-Object { $_.Trim() }

    #  Get the full file as a single string
    $File = Get-Content -Path $Path -Raw

    #  Tweak it as needed
    $File = $File.
        Replace( $ParentArray, '@(' ).
        Replace( $ArrayItem, '[pscustomobject]@{' ).
        Replace( '}', '},' ).
        Replace( '= yes', '= $True' ).
        Replace( '= no', '= $False' )

    #  Tweak the stuff at the end
    $File = $File.Trim( " },`n`r`t" ) + ' } )'

    #  If expression is safe to run
    If ( Validate-Expression $File )
        {
        #  Run the expression
        Invoke-Expression -Command $File
        }
    }

#  Import sprites
$Sprites = Import-WeirdFile -Path 'C:\Temp\sprites.txt'