bivouac,
You were almost there. You have a couple of issues.

• You show that you are using strictures, but you do not properly declare $contents
• You do not append to the value of $contents, you overwrite it each iteration

Try the following instead:

#!/usr/bin/perl
use strict;
use warnings;
use Mail::Mailer;

my %hash = (foo => '3.14159265358', bar => '1.61803398874');
notify( \%hash );

sub notify {
    my $hash_ref = shift;  
    my $mailer = Mail::Mailer->new("sendmail");
    $mailer->open( {
           From    => 'system@system.com',
           To      => 'me@system.com',
           Subject => 'Warning',
    } ) or die "Can't open sendmail : $!";

    for my $key ( keys %{ $hash_ref ) ) {
        print $mailer "$key : $hash_ref->{$key}\n";
    }
    $mailer->close();
}
[download]

Cheers - L~R