Hash default -- what's going on here?

[...]
Sigh. Hardly a novel gotcha, but I fell right into it.

Not sure of the best way to do what I want -- maybe just use
'has_key?'
and then do the right thing.
          -- Pete --

maybe

listA=["line1","line2","line3"]
listB=["line5","line3","line4"]

puts(listA & listB)

#=> line3

?

cheers

Simon