String eval is often used for dynamic code generation. For instance,
Moose uses it heavily, to generate inlined versions of accessors and
constructors, which speeds code up at runtime by a significant amount.
String eval is not without its issues however - it's difficult to
control the scope it's used in (which determines which variables are in
scope inside the eval), and it's easy to miss compilation errors, since
eval catches them and sticks them in $@ instead.

This module attempts to solve these problems. It provides an
eval_closure function, which evals a string in a clean environment,
other than a fixed list of specified variables. Compilation errors are
rethrown automatically.
