Intelligant file search for firefox

I want to use a grep like search routine in firefox's search file dialogue i.e. I want to click on 4chan's 'Search' buttan and be presented with a field where I enter 'cat' and I will be shown a list of files that have the pattern 'cat' somewhere in the filename. Any ideas on how to implement such a feature. Better yet, does anyone know an existing firefox extension that is able to do this?

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