Intercommunication between Perl and C

What should I do if I need an intercommunication between a perl and c program ? Are there any examples I could follow , or what books I should read ? I'm confused...

How can I make my CGI script more efficient when I have to call a C programme using system?

In my script there is a external C programme , I have to call it every time when the script runs . But the C programme needs to load big dictionary , the time consuming is more than 5 seconds . What should I do to make it more efficient , could I modify the C programme so that when it runs for the