#include <MsgBoxConstants.au3> ; to declare the Constants of MsgBox
Local $sRegex = "(?mu)(?:\G(?!\A)|'prices'=>\[)[\d.]*\K\h+"
Local $sString = "array('test'=>'text', 'prices'=>[16.11 19.22 21.33]);" & @CRLF & _
"array('test'=>'text', 'prices'=>[17.11 23.22 25.33 27.55]);" & @CRLF & _
"array('test'=>'text', 'prices'=>[18.11 26.22]);"
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