@parts=split/(?=\(|\))/;
print for @parts;

##</code><code>##

Using a
(
( modified yeast
( in PCNA promoter
)
) one-hybrid
( screen
)
) to identify potential
( SRF cofactors
) in cell

##</code><code>##

for(/(?:^|\(|\))[^()]*/g)
{
  print # or some processing
}