How would I change this code so it opens all my .txt files one after another (they are numbered sequentially).

In a Bourne-like command shell (like bash), you could do:

for i in *txt; do platon -c $i; done
[download]

In Perl on a Unix box (or a shell that expands the command line arguments for you), this should work:

for my $infile (@ARGV){
   next unless -e $infile;
   system("platon -c $infile"); 
}
[download]

This program expects to be passed the whole list of files to process, like this (assuming this code above is in a file called 'batch.pl'):

$ perl batch.pl *.txt
[download]

The -e file test operator attempts to make sure that the argument to be processed is an existing file. This is a small attempt to prevent a rogue user from abusing your script. In your environment security may not be an issue, but this sanity check is easy to do.

I don't understand how the $out_filename argument is used in your code, so I've silently ignored it (well, not so silently, I guess :-)

If I were on a Unix system, I'd opt for the small bit of shell script magic to drive your platon program. Of course, I may not be understanding some of your requirements (i.e. do the source files need to be executed in a particular order? Must existing outfiles not be overwritten?, etc). Of course, Perl is great for bring a Unix-like environment to a non-Unix OS. I've done a bit of Perl scripting on NT boxes and Perl has really saved me a lot of MSDOS batch language pain.

Hope this helps.