$tmpl->param(loopname => [
    {
        anothervariable => 'foo',
        foo             => 'actual value',
    },
    ...
])

##</code><code>##

$tmpl->param(loopname => [
    {
        
        fixed_key => 'actual value',
    },
    ...
])

##</code><code>##

my $new = { fixed_key => $old->{$old->{anothervariable}} };