while (<DATAFILE>) {
   unless (m{^(.*?)\s*,([\d:]+)}) {
       warn "$.: unrecognizable line: $_";
       next;
   }
   my $data = $1;
   my $time = $2;
   # ... continue processing ...
}
# output follows:
__END__
1.4567,11:00:00
1.4571,11:00:01
3: unrecognizable line:             ,             
1.4567,11:58:00
5: unrecognizable line: 1.4566 , 
1.5555,11:43:00
7: unrecognizable line: