Because ($path, $value) is a list, you get the list of submatches (list context). But if you do something like:

if ($row =~ /(.*),(.*)/)
{
  ... 
}
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since the if expects a boolean, the operation will return true if something matches, and false otherwise (boolean context). And you can still access the left and right part as $1 and $2. So you can do:

my $path = $row; # path is the full string by default
if ($row =~ /(.*),(.*)/)
{
  my $left_part = $1;
  my $value = $2;
  # Check if $value is a number and change $path if needed
  ...
}
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