#top of file
use Data::Dumper

# rest of code
print Dumper \%hash_i_want_to_look_at;
# this prints a nice representation of the data in the hash to STDOUT
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I would give you a more specific solution, if you pare your code down to where you want to view the hash, instead of posting this large section of code.

Check out How (Not) To Ask A Question, and more specifically this section. Following those guideline, helps us give you better answer.

Last time I asked a question, people complained that I didn't show all the code, so I thought it best to do it this time. Seems like its a case of damned if I do, damned if I don't eh?
Basically I was after a function that I could call from the command line to print out all the words in a particular category:


# show the words of a classification
sub show_classification
{
my ( $category ) = @_;
 #for each word in the matching category, print the word
}
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You'll get a nack for what works when asking questions. As an exercise, read other's questions and try to answer them (you don't have to answer, if you don't want). You'll quickly see how to think like someone trying answer a question - and what they need to answer it quickly.

What I would've done asking this question: Go to the data. You want to look inside %words. So I would have posted the sub classify which uses %words and the TIE that starts the hash %words. The problem being is you're asking at a perl site - so you should figure some of us have an understanding of perl. But we don't know your data.

To your question:
Take the keys of the %words and split them on '-'.

## UNTESTED
use Data::Dumper;
my %cats;
foreach my $cat_word (keys %words) {
  my ($cat,$word) = split(/-/,$cat_word);
  push(@{$cats{$cat}},$word);
}
print Dumper \%cats;
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There you should have a hash %cats with the words that are in each cat.

As for adding that into your program and printing it nicer than Data::Dumper, I'll leave that up to you.



grep

One dead unjugged rabbit fish later

As the category/word combinations are being stored in the hash combined into each key:

# from your add_words() sub
...
   $words{"$category-$word"} += $words_in_file{$word};
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You cannot make use of the main feature of hashes (O(1) lookup), and you will instead have to iterate the keys of the hash, break them into their components and the print the word if the category matches.

sub show_classification{
    my ( $wantedCategory ) = @_;

   #for each word in the matching category, print the word
    for my $key ( keys %words ) {
        my( $category, $word ) = split '-', $key;
        print "$word\n" if $category eq $wantedCategory;
    }
}
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Thanks BrowserUK! I don't fully understand it, but I'll sit down with my perl book now and figure out what you've done. cheers!

I don't think Data::Dumper would help in terms of inspecting the contents of the DB file. (thanks for the correction, grep) If you would like a plain-text (flat-table) dump of the DB file contents, something like this would do:

use strict;
use DB_File;

# Hash with composite key strings: $words{category-word} gives count o
+f
# 'word' in 'category'.  Tied to a DB_File to keep it persistent.

my %words;
tie %words, 'DB_File', 'words.db';

open( TXT, '>', 'words.txt';

while ( my ($key, $value) = each %words ) {
    print TXT "$key\t$value\n";
}
close TXT;
untie %words;
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Loading the DB file contents into an in-memory data structure shouldn't be a problem for this kind of app, in case you want to do things like sorting, or working out how many categories are associated with each word, etc.

If there's something in particular you want to do with the data that you can't figure out, give us a clearer idea of what that might be (and your first try at a solution).

Data::Dumper works just fine on Tied hashs.

use strict;
use warnings;
use Data::Dumper;

use DB_File;

my %words;
tie %words, 'DB_File', 'words.db';

load() if $ARGV[0];

print Dumper \%words;

sub load {
  my $cnt = 1;
  foreach my $key ( 'John Cleese', 'Graham Chapman', 'Eric Idle', 'Ter
+ry Jones', 'Michael Palin') {
    $words{$key} = "Gumby $cnt";
    $cnt++;
  }
}
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grep

One dead unjugged rabbit fish later

But... what if the DB file is really big? (Sometimes people tie a hash to a DB file because of the amount of data, not just for persistence.) When I tried the following test:

perl -MDB_File -MData::Dumper -e 'tie %h, "DB_File", "junk.db"; 
for ($i=0; $i<1_000_000; $i++) { $h{"key_$i"}="value_$i" };
warn "the hash is loaded\n"; sleep 15; warn "starting dump\n"; 
print Dumper(\%h); warn "the hash has been dumped\n"; sleep 15' > /dev
+/null
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Memory usage stayed at about 27 MB (macosx/perl 5.8.6) while the hash was being built and throughout the first sleep, then climbed over 450 MB during the Dump phase. Data::Dumper was making its own internal copies of the keys and values.

(The "junk.db" file itself was 47 MB, and a plain-text print out of keys and values as I suggested above would probably be about half that.)