sub main
{
   # read arguments
    ... 
   # process arguments
    ...
   # open a file
    ...
   # process the file
    ...
   # open output file
    ...
   # write output file
    ...
   # clean up temporary files
    ...
   # exit
}

##</code><code>##

sub main
{
   my %args = read_arguments();
   process_args( \%args );
   my $file = open_file( \%args );
   my $data = process_file( $file, \%args );
   write_output( $data, \%args );   
   cleanup( $file, \%args );
}