my $cgi = CGI::Minimal->new;
my $action = $cgi->param("action");

for( $action ) {

    /list_all_users/ and do {
        # either a function call or more code here
	last;
    };

    /add_user/ and do {
        # either a function call or more code here
	last;
    };
	
    /edit_user/ and do {
        # either a function call or more code here
        last;
    };

    # and so on
} 

# code to output resulting web page