Line seven sets and exports the environment variable PERL5LIB in the bash login shell configuration. That is the part which tells Perl where else to look for modules. Technically, Perl adds the path in $PERL5LIB to @INC. The perlrun and perlvar docs tell all.
The following line sources ~/.bash_profile in the current shell so that Perl has the benefit of PERL5LIB right away. That amounts to rereading the shell config.
That may fail to influence a web server's Perl environment. If it does, you can use the SetEnv directive in .htaccess or the server configuration for regular cgi scripts. I think PerlSetEnv should work for mod_perl, but mod_perl usually implies enough control that a private perl lib is unnecessary, so I've never tried that setup.