For simple programs you can easily write your own Perl routines and subroutines. As the tasks to which you apply Perl become more difficult, however, sometimes you'll find yourself thinking, "someone must have done this already." You are probably more right than you imagine.
For most common tasks, other people have already written the code. Moreover, they've placed it either in the standard Perl distribution or in the freely downloadable CPAN archive. To use this existing code (and save yourself some time), you'll have to understand how to make use of a Perl library. This was briefly discussed in Chapter 19.
One advantage in using modules from the standard distribution is that you can then share your program with others without their having to take any special steps. This is because the same standard library is available to Perl programs almost everywhere.
You'll save yourself time in the long run if you get to know the standard library. There's no point in reinventing the wheel. You should be aware, however, that the library contains a wide range of material. While some modules may be extremely helpful, others may be completely irrelevant to your needs. For example, some are useful only if you are creating extensions to Perl.
To read the documentation for a standard module, use the man or perldoc program (if you have them), or perhaps your web browser on HTML versions of the documentation. If all else fails, just look in the module itself: the ...