Assuming that there are no commas in your data other than those separating the params, I would split the lines on /\s*,\s*/, which would give you an array of your parameters, then loop through the parameters and match each of them. ie (warning, untested code)

while (<>) {
  my @params = split /\s*,\s*/;
  foreach my $param (@params) {
    $param =~ /(Identities|Positives|Negatives)\s+=\s+(.+)\s+\((.+)\%\
+)/;
    # $1 now contains which type you matched, $2 and $3 are the submat
+ches, do what you will with them
  }
}
[download]

or you could get fancier and do:

while (<>) {
  my %params = map {
    my ($k,$v) = split /\s*=\s*/;
    $v =~ /(.+)\s+\((.+)\%\)/;
    ($k => [$1,$2])
  } split /\s,\s*/;
}
[download]

and get a hash of all your params in one fell swoop.