?repeats the group contents below at most once:
.?optionally matches any character (except for line terminators)
\w+any word character, repeated at least once
the literal (3210 / 408 / 2016)
\d+a digit, repeated at least once
?optionally matches the literal (3210 / 408 / 2016)
Group 5(litros?|u(ni)?ds|kg|g) litrothe literal text litro (case insensitive) s?optionally matches the literal s (11510 / 1638 / 7316) (case insensitive)
uthe literal u (11710 / 1658 / 7516) (case insensitive)
?repeats the group contents below at most once:
nithe literal text ni (case insensitive) dsthe literal text ds (case insensitive) kgthe literal text kg (case insensitive) gthe literal g (10310 / 1478 / 6716) (case insensitive)