Passing \AtBeginDocument{...} to latexmk

Question

I need to compile with this string (this question is related to this other):

latex '\AtBeginDocument{\newcounter{MyFootnote} \let\MyOldFootnote\footnote \renewcommand{\footnote}[1]{\stepcounter{MyFootnote}\label{FootnoteMark\arabic{MyFootnote}}\MyOldFootnote{\label{FootnoteText\arabic{MyFootnote}}#1}}} \input{myfile.tex}'

(I'm sorry but I don't know hot to diplay it in a more readeble way...)

But it would be better if I could use latexmk instead. I tried:

latexmk -latex="\AtBeginDocument{\newcounter{MyFootnote} \let\MyOldFootnote\footnote \renewcommand{\footnote}[1]{\stepcounter{MyFootnote}\label{FootnoteMark\arabic{MyFootnote}}\MyOldFootnote{\label{FootnoteText\arabic{MyFootnote}}#1}}}" myfile.tex

but it doesn't work.

Here's a MWE:

\begin{document}

\setcounter{section}{4}

\section{Section}

Some dummy text.\footnote{Some dummy text.}

\end{document}