xEdit script that will change prefixes or suffixes on the EditorID field of every selected record.

Change prefix or suffix to Editor ID.pas

{
  This script will change prefixes or suffixes on the EditorID field
  of every selected record.
  
  Doesn't modify records that already have the correct prefix/suffix.
}
unit UserScript;

var
  DoPrepend: boolean;
  oldFix: string;
  newFix: string;
  
function Initialize: integer;
var
  i: integer;
begin
  Result := 0;
  // ask for prefix or suffix mode
  i := MessageDlg('Prepend [YES] or append [NO] to Editor ID?', mtConfirmation, [mbYes, mbNo, mbCancel], 0);
  if i = mrYes then DoPrepend := true else
    if i = mrNo then DoPrepend := false else begin
      Result := 1;
      Exit;
    end;
  // ask for old prefix/suffix
  if not InputQuery('Enter', 'Old Prefix/suffix', oldFix) then begin
    Result := 2;
    Exit;
  end;
  // ask for new prefix/suffix
  if not InputQuery('Enter', 'New Prefix/suffix', newFix) then begin
    Result := 2;
    Exit;
  end;
end;

function Process(e: IInterface): integer;
var
  elEditorID: IInterface;
  regexp: TPerlRegEx;
begin
  elEditorID := ElementBySignature(e, 'EDID');
  
  if Assigned(elEditorID) then
    if DoPrepend then begin
      regexp := TPerlRegEx.Create;
      regexp.Subject := GetEditValue(elEditorID);
      regexp.RegEx := '^(' + oldFix +')(.*)$';
      if regexp.MatchAgain then begin
        AddMessage('Changing ' + Name(e) + ' EditorID from "' + GetEditValue(elEditorID) +'" to "' + newFix + regexp.Groups[2] + '"');
        SetEditValue(elEditorID, newFix + regexp.Groups[2]);
      end
    end 
    else begin
      regexp := TPerlRegEx.Create;
      regexp.Subject := GetEditValue(elEditorID);
      regexp.RegEx := '^(.*)(' + oldFix +')$';
      if regexp.MatchAgain then begin
        AddMessage('Changing ' + Name(e) + ' EditorID from "' + GetEditValue(elEditorID) +'" to "' + regexp.Groups[1] + newFix + '"');
        SetEditValue(elEditorID, regexp.Groups[1] + newFix);
      end
    end;
end;

end.