From: "Peña, Botp" <botp@...>
Date: 2008-04-15T12:09:52+09:00
Subject: Re: surprise in sub

From: matt neuburg [mailto:matt@tidbits.com] 
# I didn't say that s was altered. I said that the string you 
# provide as the second param of sub might not be the string
# that gets substituted in - as the example demonstrates. If 
# you don't find this counterintuitive, you don't; great. But
# some people might. Those are the people I'm trying
# to help here. m.

i think the confusion stems fr the fact that sub/gsub has to reprocess/unescape the string twice

1 for the string as usual for possible escaping chars like \ and "

and 

2 for the group references like \1

note that this behaviour is present in other languages too.

it's been a long time i have *not used the string(as 2nd param) form. I have been getting used to w the block form since not only does it handles the double escaping issue/confusion but it also caters the match vars $1, $`, $& among others..

so, this one eg

irb(main):019:0> "hello".gsub(/([aeiou])/, "<\\1>")
=> "h<e>ll<o>"

now becomes this

irb(main):020:0> "hello".gsub(/([aeiou])/) {|s| "<#{s}>"}
=> "h<e>ll<o>"

or this

irb(main):026:0> "hello".gsub(/([aeiou])/) {"<#$1>"}
=> "h<e>ll<o>"

your choice though.

kind regards -botp