Regex backreferences

Mad_Mac has asked for the wisdom of the Perl Monks concerning the following question:

I have a regex to replace dashes between words with spaces, like this

$newName =~ s/(\w)-(\w)/\1 \2/g;

It works fine, but I get a warning saying

\1 better written as $1 at newstuff_rename.pl line 46.
\2 better written as $2 at newstuff_rename.pl line 42.
[download]

This seems to contradict the documentation, which says:

Although $1 and \1 represent the same thing, care should be taken to use matched variables $1 , $2 ,... only outside a regexp and backreferences \1 , \2 ,... only inside a regexp; not doing so may lead to surprising and unsatisfactory results.

Am I misunderstanding this?

EDIT

Got it. Thanks for the clarification!

Comment on Regex backreferences Select or Download Code

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Re: Regex backreferences by ikegami (Patriarch) on Mar 20, 2011 at 07:06 UTC
The replacement argument of the substitution operator is not a regular expression. You shouldn't use `\1` in it since `\1` means "match what the first set of captures captured". For example, you'd use something like the following to put brackets around repeated characters: `s/((.)\2+)/[$1]/g` [download] Update: Added example.	[reply] [d/l] [select]
Re: Regex backreferences by jwkrahn (Abbot) on Mar 20, 2011 at 07:07 UTC
`s/(\w)-(\w)/\1 \2/g` has two parts, the first part `/(\w)-(\w)/` is the regexp, and the second part `/\1 \2/` is just the same as any double quoted string so you have to use $1 and $2 here instead of \1 and \2.	[reply] [d/l] [select]