If by "logical line" you mean "anything up to a period .", you can use this regexp:

m/[^.]*\./s

If there are periods allowed within the line, you could try to match a . followed by a newline:

m/.*?\.(?=\n)/s

If you mean to do something completly different, you should be more explicit about your goals

Update: and to get all matches, use the /g modifier.