xmlmiddle(\d{19})
xmlmiddle\d{19}(?s).*?xmlmiddle(\d{19})
xmlmiddle\d{19}(?s).*?xmlmiddle\d{19}.*?xmlmiddle(\d{19})\d{19}(?<=xmlmiddle\d{19})
\d{19}(?<=(?s)xmlmiddle\d{19}.{40,200}?xmlmiddle\d{19})
\d{19}(?<=(?s)xmlmiddle\d{19}.{40,200}?xmlmiddle\d{19}.{40,200}?xmlmiddle\d{19})