For those running into the same problems I found:
Problem:
SQLcl 17.4.0.354.2224 which was released on December 22, 2017 has a couple of problems in the shipped sql.bat file for windows.
Running it results in:
- Message: "Environment variable echo on not defined"
- Message: "The input line is too long"
- SQLcl does'n start

Solution:
comment-out 4 lines in the supplied [sqlcl]\bin\sql.bat
(Add "rem " to the beginning of eachof these lines)
-
Line 37
**SET DEBUG=-agentlib:jdwp=transport=dt_socket,server=y,suspend=y,address=8000
**
-
Line 47
set echo on
This line causes the 'environment variable error'
If you really want to set echo on, turn it into:
@echo on
But then, be prepared for lots of junk echoed to screen
-
Line 77 and Line 88
Two comments, both starting with "<!-- " and ending with "-->"
These redirection symbols (< and >) cause the "input line is too long"
Result
