Deleting multiple backslashes; regex?

Anyone have a regex pattern for deleting multiple backslashes e.g., \\\\\\\

I pretty good with regex; but, be damned if I can delete them with preg_replace()

I've tried "\\\\" as the manual says

preg_replace("/\\\\/", '', $str);

preg_replace("/(\\\\)+/", '', $str);

preg_replace("/\x5C/", '', $str);

preg_replace("/\\x5c/", '', $str);

And lots of others.

stripslashes() and stripcslashes() are limited.