The array @INC contains the list of places that the do EXPR, require, or use constructs look for their library files. It initially consists of the arguments to any -I command-line switches, followed by the default Perl library, probably /usr/local/lib/perl, followed by ".", to represent the current directory. ("." will not be appended if taint checks are enabled, either by -T or by -t , or if configured not to do so by the -Ddefault_inc_excludes_dot compile time option.) If you need to modify this at runtime, you should use the use lib pragma to get the machine-dependent library properly loaded also:

        use lib '/mypath/libdir/';
        use SomeMod;
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You can also insert hooks into the file inclusion system by putting Perl code directly into @INC . Those hooks may be subroutine references, array references or blessed objects. See require for details.

Basically, it finds the tarball, downloads it, extracts the files, runs Build.PL or Makefile.PL followed by Build or Make respectively, then it runs tests and finally installs the library if tests are successful. It does the same for all the dependencies first.