#include <MsgBoxConstants.au3> ; to declare the Constants of MsgBox
Local $sRegex = "(?m)\s*\{\{source\|(?>[^{}]|(\{\{(?:[^{}]++|(?1))*}}))*}}\s*"
Local $sString = "# Test is a cool word {{source|{{nom w pc|Chantal|Bouchard}}, ''La langue et le nombril'', Presses de l'Université de Montréal (PUM), 2020, p. 174}}." & @CRLF & _
"# Test is a cool word {{source|Nicolas|Daniel, Presses de l'Université de Montréal 4}}"
Local $sSubst = ""
Local $sResult = StringRegExpReplace($sString, $sRegex, $sSubst)
MsgBox($MB_SYSTEMMODAL, "Result", $sResult)
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for AutoIt, please visit: https://www.autoitscript.com/autoit3/docs/functions/StringRegExp.htm