Purpose With  ReplaceText you can replace strings in a text variable.
Example ReplaceText "t1" from="%1" to="1245678"

All occurrences of the string "%1" in the text "t1" are replaced with "1245678".
Format ReplaceText "textvar" from="string1" to="string2"

In the text variable "textvar", all occurrences of the  from= string are replaced with the to= string.  You can then use  if Q[ok] in order to query whether at least one string replacement has been carried out.

Instead of from= you can also use fromHexCode= ; analogously toHexCode= instead of  to= . Using this notation you can specify  hexadecimal strings. Example:

GuiXT 
// delete utf8-header
ReplaceText "t1" fromHexCode="efbbbf" to=""
Components GuiXT + InputAssistant