Both athomason and knight have mentioned some good suggestions as to how to do the parsing. To address your question of how to store the data: I would go the single-global way. But as pointed out by athomason, a variable declared with "my" is not necessarily a global. The proper way would be to do something like this:

use strict;
use vars qw($program);

$program={};
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and then you can use $program anywhere in your code. Notice that I am making $program into a reference directly, because that's how it is going to be used all over the place. It will save you quite a few \%'s when calling subroutines.

If you are of the C tradition, you could have a "main" subroutine, and instead of declaring $program as global, make it my within that subroutine, which would then pass its reference to everyone else:

sub main {
  my $program;
  ...
  $program={};
  parse_program("source.c", $program);
  print_functions($program);
  do_other_stuff($program);
}
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Within the subroutines themselves, you would have to do the two levels of indexing, but I don't think that is a big deal. You can store the necessary elements in variables to use within each subroutine:

sub print_functions {
  my $program=shift; # this is not needed if $program is
                     # global, obviously
  my $functions=$program->{functions};

  # and now you can just use $functions to access the data
}
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Cheers,

--ZZamboni