Regex problem with brackets and returning a value from memory

[Chang]

I was doing a page list for my accessible EPUB 3 ebook according to these instructions (https://gold-chartreuse-795z.squares...ng-a-page-list). In one part there is Regex used:

Create the correct code for the page breaks. This RegEx string works in oXygen XML editor:
<span class="com-rorohiko-pagestaker-style">(\d+?)</span>
<span epub:type="pagebreak" role="doc-pagebreak" id="page$1" aria-label=" Page $1\. " />

I tried this Regex find and replace search in Sigil and it doesn't seem to work. When I use this same Regex string in Sigil's Regex search, all I get is this:

<span epub:type="pagebreak" role="doc-pagebreak" id="page$1" aria-label=" Page $1\. " />

Seems that in Sigil nothing is saved in memory when using brackets. Is there some other way to do this in Sigil? I know in the instructions Sigil is not used for this part but I would like to know why this regex string is not working in Sigil.

[Chang]

I just found a solution for my problem and it seems that I'm not able to delete my post anymore.

Instead of $1 I need to use \1 in Sigil to return the value from the memory.

Sorry for posting too hastingly!

[DNSB]

You may want to practice RegEx on RegEx 101. Use the PCRE2 flavour of RegEx for Sigil practice. The $1 suggests an ECMAscript/Javascript flavour of RegEx.

[Capricorn]

Hmmmm.....I am confused now. I did a little test:
I put this regex into the regex101 machine, using PCRE2: <span>([^<>]*)</span>
Regex101 then tells me there is a mistake and I need to change it to:
<span>([^<>]*)<\/span> notice the backslash in the closing span

However, when I use <span>([^<>]*)</span> - without the backslash, in Sigil v2.3.1 (running on win11 pro, build 22631.4169), it works perfectly. Hence, my question: Is the regex of Sigil a variant of PCRE2 or...?
As I am not an expert on regex, but still like to use it, I am trying to understand what is going on.

And on this page https://sigil-ebook.com/sigil/ it says it uses PCRE

And when I use python on regex101 instead of PCRE or PCRE2, it does not need a backslash either.

Hmm.....yes, definitely confusing............