There are now three commands one can use to interact with value expressions
directly:
ledger parse EXPR # shows the parse tree resulting from EXPR
ledger compile EXPR # shows what the compiled tree looks like
ledger eval EXPR # print the resulting value, useful in scripts
old system (for example, the meaning of 'a') has yet to be restored. In the
new scheme, this will be done by definition a function outside of the value
expression logic, rather than the tight coupling between journal innards and
value expressions that occurred in 2.x.