how to pass a hash along with other arguments to a subroutine in perl?

my code:

$self->commitToPerforce($network_name[0], {"size_of_table=>$row->{numRecords}"});

sub commitToPerforce {
    my $self = shift;
    my $network = shift;
    my %metadata = shift;

    open my $FH, ">$local_metadata_file" || die "Could not open file $local_metadata_file";
    print $FH Dumper(%metadata);
    close $FH;
}

problem is, this is what's getting into the file:

$VAR1 = 'HASH(0x320adf0)';
$VAR2 = undef;

not what I'm looking for.

Also tried this:

print $FH Dumper(\%metadata);

which just gives me this:

$VAR1 = {
      'HASH(0x223cea0)' => undef
    };

I want the contents of the hash. Not the reference to the hash.

getting closer now:

my $hash = {"size_of_table=>$row->{numRecords}"};
$self->commitToPerforce($network_name[0], $hash);

   open( my $FH, ">", $local_metadata_file ) || die "Could not open file $local_metadata_file";
print $FH Dumper($metadata);
close $FH;

results in:

 $VAR1 = {
      'size_of_table=>0' => undef
    };

what's with the 'undef'??

oh. i see it now. my hash should not be a single string.

and just because there's no where else for me to gripe: why is it a good idea to spend so much time thinking about my data structures in this way?

Solution

Here are some comments on your code

I hope the call to commit_to_perforce is in a different file from the method definition?
It is often much clearer to define a hash parameter separately and then pass a reference to it, rather than passing an anonymous hash directly in the parameter list
Within a method, it is usually best to shift the vlaue of $self off the parameter list, and then do a list assignment for the rest of the parameters
You should use the three-parameter form of open, and either check that it succeeded with a die string that includes $! to give the reason for the failure, or just use autodie.

Because of the precedence of the || operator, your code checks the truth of the string ">$local_metadata_file" instead of the return value from open. You can either use the low-precedence or operator instead or put parentheses around the parameters to open
It is common practice to reserve upper case letters for global identifiers, such as the package Dumper. Local variables should normally be named using lower-case letters, numbers, and underscore

Taking all of that into account, here's how your code should look

my %meta = (
  size_of_table => $row->{numRecords},
);

$self->commit_to_perforce($network_name[0], \%meta);

sub commit_to_perforce {
  my $self = shift;
  my ($network, $metadata) = @_;

  open my $fh, '>', $local_metadata_file
      or die "Could not open file '$local_metadata_file' for output: $!";
  print $fh Dumper $metadata;
  close $fh;
}

I hope this helps