$ perl   -an '-F/\|\|\|/'  -e 'm/\d/ or do{print qq<$k|||$v|||\n> ;$k=$v="";next};$k=$F[0];$v.=$F[1].qq|;|' data2.txt 
21997|||70049,,20170428154818,20170527235959;70070,,20170428154739,20170527235959;|||
21998|||70049,,20170428154818,20170527235959;70070,,20170428154739,20170527235959;70071,,20170428154739,20170527235959;|||