Group-ObjectFast: Compatibility with standard Group-Object

[scriptingstudio]

If you group multiple properties standard Group-Object uses ", " (comma + space) as delimiter in the Name field.
Line 42 has an error in join operator argument

$key = $(foreach($_ in $Property) { $InputObject.$_ }) -join ','

It should be

$key = $(foreach($_ in $Property) { $InputObject.$_ }) -join ', '

Test

$data = ConvertFrom-Csv @'
Region,Item,TotalSold
South,melon,47
South,orange,84
West,hammer,81
South,nail,62
East,lime,74
West,pear,88
East,drill,26
South,saw,42
East,kiwi,46
North,banana,2
'@ 

$data | Group-Object Region,item 
Count Name                      Group                                                                                         
----- ----                      -----                                                                                         
    1 South, melon              {@{Region=South; Item=melon; TotalSold=47}}                                                   
    1 South, orange             {@{Region=South; Item=orange; TotalSold=84}}                                                  
    1 West, hammer              {@{Region=West; Item=hammer; TotalSold=81}}                                                   
    1 South, nail               {@{Region=South; Item=nail; TotalSold=62}}                                                    
    1 East, lime                {@{Region=East; Item=lime; TotalSold=74}}                                                     
    1 West, pear                {@{Region=West; Item=pear; TotalSold=88}}                                                     
    1 East, drill               {@{Region=East; Item=drill; TotalSold=26}}                                                    
    1 South, saw                {@{Region=South; Item=saw; TotalSold=42}}                                                     
    1 East, kiwi                {@{Region=East; Item=kiwi; TotalSold=46}}                                                     
    1 North, banana             {@{Region=North; Item=banana; TotalSold=2}}

Moreover, it works incorrectly with multiple properties

$data | Group-ObjectFast -Property Region,item
Count Name         Group                                       
----- ----         -----                                       
    1 North,banana {@{Region=South; Item=nail; TotalSold=62}}  
    1 North,banana {@{Region=East; Item=drill; TotalSold=26}}  
    1 North,banana {@{Region=West; Item=hammer; TotalSold=81}} 
    1 North,banana {@{Region=South; Item=saw; TotalSold=42}}   
    1 North,banana {@{Region=West; Item=pear; TotalSold=88}}   
    1 North,banana {@{Region=South; Item=melon; TotalSold=47}} 
    1 North,banana {@{Region=East; Item=kiwi; TotalSold=46}}   
    1 North,banana {@{Region=East; Item=lime; TotalSold=74}}   
    1 North,banana {@{Region=North; Item=banana; TotalSold=2}} 
    1 North,banana {@{Region=South; Item=orange; TotalSold=84}}