#include <MsgBoxConstants.au3> ; to declare the Constants of MsgBox
Local $sRegex = "(?mi)([0-9A-F])([0-9A-F])([0-9A-F])([0-9A-F])([0-9A-F])([0-9A-F])([0-9A-F])([0-9A-F])\-([0-9A-F])([0-9A-F])([0-9A-F])([0-9A-F])\-4([0-9A-F])([0-9A-F])([0-9A-F])\-([0-9A-F])([0-9A-F])([0-9A-F])([0-9A-F])\-([0-9A-F])([0-9A-F])([0-9A-F])([0-9A-F])([0-9A-F])([0-9A-F])([0-9A-F])([0-9A-F])([0-9A-F])([0-9A-F])([0-9A-F])([0-9A-F])"
Local $sString = "D01A42F5-FD89-4c8f-8065-726AD4363411"
Local $sSubst = "$31$1$30$2$29$3$28$4-$27$5$26$6-4$25$7$24-$8$23$9$22-$10$21$11$20$12$19$13$18$14$17$15$16"
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