How can I keep the current language prefix for internal link? If the links are menu items the destinations of the links are always with the language inherited from the previous pages. But how can I do the same thing for the internal links using ordinal &lt;a href=""&gt; tags?  I have some internal links in some blocks but those links can't keep the language prefix the use is currently viewing of. 
For example:

&lt;a href="/about-us"&gt; takes the user to my-site.com/about-us though the user is currently viewing the page with the language prefix "jp" which is Japanese. But I would like to make the destination of the link to my-site.com/jp/about-us.

I've been searching for the solution for days but no luck so far. I have tried pathfilter and pathologic but they don't seem to work for this purpose.
Generally you want to use Drupal core functions as much as possible. Both the l() and url() functions fit perfectly your need. The difference between them is that l() returns an anchor tag, and url() returns a URL without HTML.

As a perk, the l() function allows you to specify the language for the link. Example:

&lt;?php
$options = array('language' =&gt; 'jp');
$link = l('About Us', 'about-us', $options);