Take SYS_FBA_TCRV_IDX1_36953 SYS_FBA_TCRV_36953 and pull out SYS_FBA_ and _36963

It captures the ESIC number explained which format is explained here https://www.quora.com/How-is-the-format-of-the-ESIC-code.

matches the format of EPF number. For further details visit here https://www.bankbazaar.com/saving-schemes/all-about-the-employee-pf-account-number.html#format

NSW is different to other states (see red text)

To remove @recipient and other funny characters

A variety of BEM flavoured regex.

Matches a string of digits between 0 and 255.

Matches a string of digits between 0 and 255.