For example, Vimeo generates following code for embedding video:

<object width="400" height="300"><param name="allowfullscreen" value="true" /><param name="allowscriptaccess" value="always" /><param name="movie" value="http://vimeo.com/moogaloop.swf?clip_id=6528299&amp;server=vimeo.com&amp;show_title=1&amp;show_byline=1&amp;show_portrait=0&amp;color=&amp;fullscreen=1" /><embed src="http://vimeo.com/moogaloop.swf?clip_id=6528299&amp;server=vimeo.com&amp;show_title=1&amp;show_byline=1&amp;show_portrait=0&amp;color=&amp;fullscreen=1" type="application/x-shockwave-flash" allowfullscreen="true" allowscriptaccess="always" width="400" height="300"></embed></object><p><a href="http://vimeo.com/6528299">Grizzly Bear - While You Wait for the Others</a> from <a href="http://vimeo.com/grandchildren">Grandchildren</a> on <a href="http://vimeo.com">Vimeo</a>.</p>

If you'll put this code to MLF's "Insert flash video" form and submit,
MLF-parser will make from it such code:

[flash width=400 height=300]true[/flash]

For best result you need to insert movie's URL & parameters from Vimeo's code tag

<embed src="...">

to MLF-parser's code instead word "true":

[flash width=400 height=300]http://vimeo.com/moogaloop.swf?clip_id=6528299&server=vimeo.com&show_title=1&show_byline=1&show_portrait=0&color=&fullscreen=1[/flash]

...and after submitting your new message you'll see this:

Enjoy! :)