I don't know of any existing tools like this.
However, there is a really cool toolkit for doing regular
expressions in the new ActiveState Komodo interface. You
can type in a regexp and some text to match. It
highlights what is currently being matched and explains
what is going on in English. You can advance through each
part of it and it shows what is getting stored in each
of the variables $1, $2 etc.
This might at least help with one aspect of perl although
a general tool might be a great learning aid as you mention.