catchfilebetweentags error with multicol

Question

I am using the catchfilebetweentags library to store equations in an external file and then import them into my document. This is useful when you need to use the same equation in multiple documents. This works for simple equations, but introduces an offset error when used with the multicols package. Does anyone know of a solution to this problem?

MWE

main.tex

\documentclass{article}
\usepackage{amsmath}
\usepackage{catchfilebetweentags}
\usepackage{multicol}

\newcommand{\loadeq}[1] {
    \ExecuteMetaData[./equations.tex]{eq#1}
}

\begin{document}

Loading equations from external file:
\loadeq{001}

Local equations:
\begin{multicols}{2}
    \begin{equation}
        \label{equ:X2}
        X = 
        \begin{bmatrix}
            X_0 \\
            X_1 \\
            X_2 \\
            X_3
        \end{bmatrix}
    \end{equation}

    \begin{equation}
        \label{equ:Y2}
        Y = 
        \begin{bmatrix}
            Y_0 \\
            Y_1 \\
            Y_2 \\
            Y_3
        \end{bmatrix}
    \end{equation}
\end{multicols}

\end{document}

equations.tex

\documentclass{article}
\begin{document}

%<*eq001>
\begin{multicols}{2}
    \begin{equation}
        \label{equ:X}
        X = 
        \begin{bmatrix}
            X_0 \\
            X_1 \\
            X_2 \\
            X_3
        \end{bmatrix}
    \end{equation}

    \begin{equation}
        \label{equ:Y}
        Y = 
        \begin{bmatrix}
            Y_0 \\
            Y_1 \\
            Y_2 \\
            Y_3
        \end{bmatrix}
    \end{equation}
\end{multicols}
%</eq001>

\end{document}

Answer 1

The problem is that catchfilebetweentags ignores blank lines. If you remove the blank line in the “local” part, you get exactly the same.

Solution: use \par in the auxiliary file instead of a blank line.

\documentclass{article}
\begin{document}

%<*eq001>
\begin{multicols}{2}
    \begin{equation}
        \label{equ:X}
        X = 
        \begin{bmatrix}
            X_0 \\
            X_1 \\
            X_2 \\
            X_3
        \end{bmatrix}
    \end{equation}
\par
    \begin{equation}
        \label{equ:Y}
        Y = 
        \begin{bmatrix}
            Y_0 \\
            Y_1 \\
            Y_2 \\
            Y_3
        \end{bmatrix}
    \end{equation}
\end{multicols}
%</eq001>

\end{document}

However, using multicol to show equations side by side is not the best method, I'd go for two minipages.