'reaction' => [
                        {
                          'substrate' => {
                                         'name' => 'cpd:C00084'
                                       },
                          'name' => 'rn:R00710',
                          'product' => {
                                       'name' => 'cpd:C00033'
                                     },
                          'type' => 'reversible'
                        },                       {
                          'substrate' => [
                                         {
                                           'name' => 'cpd:C00068'
                                         },
                                         {
                                           'name' => 'cpd:C00022'
                                         }
                                       ],
                          'name' => 'rn:R00014',
                          'product' => {
                                       'name' => 'cpd:C05125'
                                     },
                          'type' => 'irreversible'
                        },

##</code><code>##

$data = $xml->XMLin($input_file);

foreach $g (@{$data->{reaction}})
{
        foreach $h ($g->{substrate}){
                $temp1 = $h->{name};
                foreach $i ($g->{product}->{name}){
                      $temp2 = $i->{name}
                      print "$temp1 -- $temp2\n";
                }
        ]
}