Perpendicular symbol with litle square

Question

How can I insert this symbol in math environment? \Thanks

Answer 1

Currently, I have only set it up for \displaystyle. If you need smaller math styles, let me know.

One can change the square size with \sqdim.

\documentclass{amsart}
\usepackage{stackengine}
\def\sqdim{.4ex}
\newcommand\perpsq{\mathrel{\ensurestackMath{\stackengine{0pt}{\perp}
  {\kern\sqdim\rule[\sqdim]{\sqdim}{.4pt}\rule[.4pt]{.4pt}{\sqdim}}{O}{c}{F}{F}{L}}}}
\begin{document}
$A \perpsq B$
\end{document}

Here with \sqdim set to .3ex: