Can someone explain this regexp command?

I have some code:

expr = '<Placemark>.*?</Placemark>';

objectStrings = regexp(txt,expr,'match');

This works exactly as I would like it to. However, I am not fundamentally understanding what Matlab is doing, specifically when I see the .*? I have pored over the documentation, but I am just not understanding. Would someone please be kind enough to explain what is happening?

[KSSV]

What is txt in the input of regexp?

Answer 1

[Stephen23]

It is quite simple:

<Placemark>                % match literal string
           .*              % match any characters, any number of times
             ?             % makes the previous quantifier lazy (ie *)
              </Placemark> % match literal string

The MATLAB documentation explains how regular expressions work:

https://www.mathworks.com/help/matlab/matlab_prog/regular-expressions.html

And we find it explains all of those parts of your regular expression:

• angle brackets are not special characters, therefore the "placemark" parts are interpreted literally.
• " expr* 0 or more times consecutively."
• " exprq? Lazy expression: match as few characters as necessary."