$l2h_cache_key = q/$$\partial_t \eta (t) = g(\eta(t),\varphi(t))$$ ''/;
$l2h_cache{$l2h_cache_key} = q|
”|;
$l2h_cache_key = q/$--a {\frac{1}{2}} @minus{}$/;
$l2h_cache{$l2h_cache_key} = q|
|;
$l2h_cache_key = q/$--a@minus{} {\frac{1}{2}}$/;
$l2h_cache{$l2h_cache_key} = q|
|;
1;