etwdata=[[1,2],[3,4],[5,6]] # only example data
etwdata.each{ |rot|
rot.each{ |val|
print (val + ?A).chr," " # here ruby fails...error message
below...
}
print "\n"
Ruby's error message:
basicenigma4.rb:175: warning: don't put space before argument
parentheses
Listen to the warning 
c:\>ruby
etwdata=[[1,2],[3,4],[5,6]]
etwdata.each{ |rot| rot.each { |val| print( (val + ?A).chr, "") } }
puts
^Z
BCDEFG