1010100.........123456.....   #header line for bill # 123456
#some data
#some data
#some data
#some data
1010100.........678910.....    #header line for  bill # 678910
#some data
#some data
#some data
3010330.........123456.....   #bill detail for bill 123456
#some data
#some data
#some data
#some data
#some data
3010330.........678910.....   #bill detail for bill 678910

For eg. each bill should be split and joined like this:
1010100.........123456.....   #header line for bill # 123456
#some data
#some data
#some data
#some data
3010330.........123456.....   #bill detail for bill 123456
#some data
#some data
#some data
#some data
#some data
<br>