SQL & PL/SQL

Hi Guys, hoping somone could give me a PL SQL example to solve the problem below:

TABLE 1 NAME = CHEESE
COLUMNS = BLUE, SWISS, RED

TABLE 2 NAME = JUICE
COLUMNS = APPLE, PEAR, GRAPE

TABLE 3 NAME = BISCUIT
COLUMNS = CRACKER, CHOCOLATE


UPDATE [TABLE 1]
SET [1st COLUMN SPECIFIED FOR TABLE 1] = REPLACE([1st COLUMN SPECIFIED FOR TABLE 1], 'abc', 'xxx')
WHERE [1st COLUMN SPECIFIED FOR TABLE 1] LIKE '%abc'
OR [1st COLUMN SPECIFIED FOR TABLE 1] LIKE 'abc%'
SET [1st COLUMN SPECIFIED FOR TABLE 1] = REPLACE([1st COLUMN SPECIFIED FOR TABLE 1], 'ABC', 'YYY')
WHERE [1st COLUMN SPECIFIED FOR TABLE 1] LIKE '%ABC'
OR [1st COLUMN SPECIFIED FOR TABLE 1] LIKE 'ABC%'

(Repeat for TABLE 2)
(Repeat for 1st COLUMN SPECIFIED for TABLE 2)

(Go on to TABLE 3)
(Repeat etc)

Could somone show me the simplest way to achieve this in PL SQL?

Cheers!