As long as the perennial isn't directly over the bulbs, it's not a problem. I have peonies and daffodils all mixed up together, and by the time the daffodils are done, the peonies are getting bigger, and I don't have to look at flopping over daffodil foliage anymore.

I don't plant annuals, as it's too much work year to year, but I have lavendar in my rose garden, and several different perennials, as well as more daffodils, in my shrub bed.

I recommend that you get yourself a good overall gardening book - try the library first to see if you like any of them- as most of them will have an explanation of planting a mixed border, which I think is what you're looking for.

Have fun mixing it up!

Perennials and bulbs can coexist very nicely together. As can perennials, shrubs, grasses, groundcovers and annuals. Even some trees can be included into the mix. This is what's known as a mixed border and it offers the opportunity to have planting areas with year round interest and also the ability to develop planting areas that have both permanent 'bones', volume and a variety of heights.

All you really need to consider is the suitability of the plants being grown together and ultimate sizing. Suitability means plants that share the same growing conditions as far as soil, water and light. For example, while roses and lavenders are a popular combination in theory, they do not share the same growing requirements except for a love of sun and growing them in close proximity means one or the other may not be receiving the best conditions to thrive.

Sizing is also a consideration, both with regards to height and spread. Generally it is considered better to put taller growing plants in the back of a planting area (or in the center, if an island) with lower growing plants towards the outside. But depending on the plant, this not a hard and fast rule -- some plants are airy enough to be in the front of the border and they do not obscure what is growing behind them.

It is important to pay attention to what is considered to be the mature spread of the plants in question as well, as that will determine the spacing. It's hard to imagine that plants purchased as starters in small pots can grow up to be large specimens but it happens! Most perennials can be divided and many shrubs can be pruned to maintain a smaller size but it is best to allow sufficient space for natural, unimpeded growth.

there is an excellent book that addresses this design situation in considerable detail - The Well-Designed Mixed Garden by Tracy DiSabato-Aust. Not only does she provide dozens of examples of planning mixed plantings of bulbs, perennials, shrubs and other plant types but she gives detailed information and care instructions on the individual plants themselves. This is an excellent resource and a great reference.