#include <MsgBoxConstants.au3> ; to declare the Constants of MsgBox
Local $sRegex = "\b(https?://\S*?/documents/)en(/\S*)\.pdf\b"
Local $sString = "The problem is, if the page contains a PDF linked to another page (not my own website), example https://othersite.example.com/whatever.pdf, it becomes https://othersite.example.com/whatever_SPANISH.pdf which isn't valid on other people's sites. I want to ignore offsite links and only change URLs on my site." & @CRLF & _
"" & @CRLF & _
"So what I would like to do is look for the string: https://example.com/documents/en/whateverfilename.pdf and pull that file name out and change it to https://example.com/documents/es/whateverfilename_SPANISH.pdf (Switching the en to es and also appending the _SPANISH to the end of the PDF filename." & @CRLF & _
"" & @CRLF & _
""
Local $sSubst = "$1es$2_SPANISH.pdf"
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