#!/usr/bin/perl -w
use strict;

package Foo;

sub new {
    bless {
        _this => "this\n",
        _that => "that\n"
    }, shift
}
sub _this { print $_[0]->{_this} }
sub _that { print $_[0]->{_that} }

package main;
my $thing = Foo->new;

runTests( $thing );

sub runTests {
    my $object = shift;
    my $pkg    = ref $object;

    no strict 'refs';
    foreach my $symname (keys %{"${pkg}::"}) {
        my $sub = "${pkg}::$symname";
        if ( defined &$sub and '_' eq substr $symname, 0, 1 ) {
            $sub->( $object ); # explicitly pass $object to mimic method call
        }
    }
}