debugger perl -d

perl -d test.pl test.txt

x [maxdepth] expr

Evaluates its expression in list context and dumps out the result in a pretty-printed fashion. Nested data structures are printed out recursively, unlike the real function in Perl. When dumping hashes, you'll probably prefer 'x \%h' rather than 'x %h'. See if you'd like to do this yourself.

The output format is governed by multiple options described under .

#!/usr/bin/perl -w
#
#use strict;

my %hash;
my %src;

while(<>){
    next if(/^#/);

    my ($src, $dst, $bytes) = split;
    $hash{$src}{$dst} += $bytes;
    $hash{$src}{"all"} += $bytes;
}
for my $source (sort {$hash{$b}{all} <=> $hash{$a}{all}} keys %hash){
#print "$source                 =>              $hash{$source}{$all}\n";
    for my $dest (sort {$hash{$source}{$b} => $hash{$source}{$a}} keys %{$hash{$source}}){
        print "    $source => $dest  $hash{$source}{$dest}\n";
    }
}

perl -d hash_hash.pl coconet.dat

 DB<1> s

  DB<2> x \%hash
0  HASH(0x9daf80c)
   'gilligan.crew.hut' => HASH(0x9e46294)
      'all' => 4721
      'lovey.howell.hut' => 4721
   'thurston.howell.hut' => HASH(0x9e46214)
      'all' => 4046
      'lovey.howell.hut' => 4046

When we give x a hash reference, it dumps the entire contents of the hash, showing the key/value pairs. If any of the values are also hash references, it dumps those as well, recursively. What we'll see is that the %hash hash has a single key of gilligan.crew.hut, whose corresponding value is another hash reference. The referenced hash contains a two keys of all , with a value of 1250 and lovey.howell.hut value of 4721.