Hi,

Use this, because with the previous the selected output for any print, write,etc will be DM, not the desired, so:

select( (select (DM), ($- = 0))[0] );
[download]

Will select again the previous output you had before calling select, but assigning the $- variable for that filehandle

But better is to use lexical variables as filehandles, in the code it seems like you have a register to asign each time, and write to a list of files, why not something like this:

for my $file (@files) {
   open my $fh, '<', $file;
   select((
      select($fh),
      $~ = "DM",
      $^ = "DM_TOP"
     )[0]
   );
   # Data adquisition stuff here
   write $fh;
}
[download]

By the way take a look at Perl6::Form, it have a lot of improvements, and not these limitations that Perl 5 formats has.

And the why this seems to happen, think it is because the DM is a global symbol, and it doesn't get reset the values automatically because when you close the filehandle the DM symbol is not erased...

Regards,