On Behalf Of Paulo Carvalho:
# I have a problem with irb console.
# When i want to write special characters like "@" and "[" or 
# "]" i cant. IRB simply dont let me write this characters. It 
# is like if i was not writing on the beyboard.

i'm assumming you do not have an english keyboard, 

try 

  irb --noreadline

kind regards -botp