while (<DATA>) {
    s/\bis\b/are/g;
    print;
}

__DATA__
Apache is a modular server. This implies that only the most basic functionality
is included in the core server. is it so ?
Extended features are available through modules which can be loaded into Apache.
 By default, a base set of modules is
included in the server at compile-time. If the server is compiled to use dynamic
ally loaded modules, then modules can be
compiled separately and added at any time using the LoadModule directive. Otherw
ise, Apache must be recompiled to add or
remove modules. Configuration directives may be included conditional on a presen
ce of a particular module by enclosing
them in an <IfModule> block.