use strict;
    use vars ('$really_global_var');
{
    # First block, the main routine
    my($var_in_main);

    main();
    exit(0);

sub main
  {
    SubOne::sub1();
    ...
  }
}

{
    # Second block for the first set of things

    # Can also put it in its own package for further
    # clarity
    package SubOne;
    my($sub1_var);

sub sub1
  {
    $::really_global_var = 42;
    $sub1_var = 23;
  }
}