As pointed out by others you don't get anything that is generally very useful when you interpolate a hash reference into a string. However, you can copy hash elements to an array and an array interpolates nicely (for some value of nice):

use strict;
use warnings;

my %people=(
    'Jones'=>{'name'=>'Alison', 'age'=>15, 'pet'=>'dog',},
    'Smith'=>{'name'=>'Tom', 'age'=>34, 'pet'=>'cat',}
    );

for (keys %people) {
    my @values = %{$people{$_}};
    print "@values\n";
}
[download]

Prints:

pet cat name Tom age 34
pet dog name Alison age 15
[download]