Program Repair Shop

Function Arguments

    18     my ($pwd,$i)=($_[0],$i++);

Let's fix this:

          my ($src,$dst) = @_;

Use $src and $dst instead of $source_directory and $target_directory
Now these hardwired variable names no longer make sense:

    19     die "You have not defined the \$target_directory variable, sorry...\n" 
             unless  -e $target_directory;
    20     die "You have not defined the \$source_directory variable, sorry...\n" 
             unless  -d $source_directory;

Let's go with

     unless (@_ == 2) { die('Usage: xcopy($src, $dst)') }

That line 20 message was wrong anyway