Replacing values in a string

Summary

How can I replace values within a string

Content

I have a process that utilises a webform, on that form a user will cut and paste a list of UK postcodes (aka US ZIP Code, but different format) into a control (text area) for example

S63 0EF
CF32 7HY
SE28 8JY
SO18 1BE
G33 5BP

 

I want to be able to take the postcode data the users entered and create a comma separated string.  So in this example I want to replace the newline character with ","  and I also want to replace the space within each postcode with a "-" to give