From: Kyle Schmitt <kyleaschmitt@...>
Date: 2007-07-20T07:23:40+09:00
Subject: regex backreference weirdness...

It all started with trying to convert some strings with underscores in
them, to camel case...and me thinking of regexes as sed regexes

It looks like gsub saves back references, but only after the whole
method exits, so it can't use what it found.  Is this right?

Below is what I tried, which leads me up to the question of... what
would the _right_ way be of doing this?

irb>"camel_case".gsub(/_(.)/,$1.upcase)
NoMethodError: undefined method `upcase' for nil:NilClass
        from (irb):1
#Which made me say Hu?  it looks like a valid back reference to me...
#So I tried
"camel_case"=~/_(.)/
irb>puts $1
=>"c"
#ok really wierd...
irb>"camel_case".gsub(/_(.)/,$1.upcase)
=>"camelCase"
#Right, I'll buy that since $1 is still hanging around
irb>"camel_face".gsub(/_(.)/,$1.upcase)
=>"camelCase"
irb>"camel_face".gsub(/_(.)/,$1.upcase)
=>"camelFase"
#Ha ha!  gsub DOES save a backreference... so why isn't this working?! :(