Can't locate object method "add" via package "Heap" - perl

Question

I'm not sure why perl isn't recognizing the Heap's method add. Getting message given in question title. Here are the most relevant files.
#!/usr/bin/perl -w
use strict;
use Util;
use Heap;
use HuffTree;
my $heap = Heap->new;
my $test = 3;
$heap->add($test); # <--------ERROR HERE-----------
package Heap;
use strict;
use warnings;
use POSIX ();
sub new {
my $class = shift;
my $self = { "aref" => [""],
"next" => 1,
#_};
bless $self, $class;
}
sub print {
my $self = shift;
my $next = $self->{"next"};
my $aref = $self->{"aref"};
print "array => #$aref\n";
print "next => $next\n";
}
sub compare {
my ($self, $i, $j) = #_;
my $x = $self->{"aref"}[$i];
my $y = $self->{"aref"}[$j];
if (!defined $x) {
if (!defined $y) {
return 0;
} else {
return -1;
}
}
return 1 if !defined $y;
return $x->priority <=> $y->priority;
}
sub swap {
my ($self, $i, $j) = #_;
my $aref = $self->{"aref"};
($aref->[$i], $aref->[$j]) = ($aref->[$j], $aref->[$i]);
}
sub add {
my ($self, $value) = #_;
my $i = $self->{"next"};
$self->{"aref"}[$i] = $value;
while ($i > 1) {
my $parent = POSIX::floor($i/2);
last if $self->compare($i, $parent) <= 0;
$self->swap($i, $parent);
$i = $parent;
}
$self->{"next"}++;
}
sub reheapify {
my ($self, $i) = #_;
my $left = 2 * $i;
my $right = 2 * $i + 1;
my $winleft = $self->compare($i, $left) >= 0;
my $winright = $self->compare($i, $right) >= 0;
return if $winleft and $winright;
if ($self->compare ($left, $right) > 0) {
$self->swap($i, $left);
$self->reheapify($left);
} else {
$self->swap($i, $right);
$self->reheapify($right);
}
}
sub remove {
my $self = shift;
my $aref = $self->{"aref"};
my $result = $aref->[1];
$aref->[1] = pop #$aref;
$self->{"next"}--;
$self->reheapify(1);
return $result;
}
sub empty {
my $self = shift;
return $self->{"next"} == 1;
}
1;
package HuffTree;
use warnings;
use strict;
use Pair;
our #ISA = "Pair";
sub priority {
my $self = shift;
# lowest count highest priority
return -$self->{frequency};
}
sub left {
my $self = shift;
return $self->{left};
}
sub right {
my $self = shift;
return $self->{right};
}
1;
package Pair;
use warnings;
use strict;
sub new {
my $class = shift;
my $self = { #_ };
bless $self, $class;
}
sub letter {
my $self = shift;
return $self->{letter};
}
sub frequency {
my $self = shift;
return $self->{frequency};
}
sub priority {
my $self = shift;
return $self->{frequency};
}
1;
package Util;
use strict;
use warnings;
sub croak { die "$0: #_: $!\n"; }
sub load_arg_file {
my $path_name = shift #ARGV;
my $fh;
open($fh, $path_name) || croak "File not found.\n";
return $fh;
}
1;

Answer 1

You have a Heap.pm installed from CPAN. That's what gets loaded, not your own Heap.pm. The new sub in the Heap.pm from CPAN looks like this:
sub new {
use Heap::Fibonacci;
return &Heap::Fibonacci::new;
}
Which is actually a bug in said module, because Heap::Fibonacci uses the
standard bless \$h, $class; thing in its new sub,
so the reference is blessed into the Heap package, which
does indeed not have a sub called add (Heap::Fibonacci does).
To solve your immediate problem, you can:
make sure that your module is picked up before the "other" Heap (by modifying #INC with use lib, for example;
or not reinvent the wheel and actually use Heap::Fibonacci).
At any rate, it might be a good idea to report this problem
to the Heap module author - because even if you did not have
your own Heap.pm, your code would still fail with the same message.