Re^2: Substitution backreference woes

Forgive me, but the working examples do not seem to cover the use of \1 (etc) in the replacement expression.

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Re^3: Substitution backreference woes by Anonymous Monk on Jan 24, 2015 at 15:30 UTC
Forgive me, but the working examples do not seem to cover the use of \1 (etc) in the replacement expression. It's covered in perlop Unlike sed, we use the \<digit> form in only the left hand side. Anywhere else it's $<digit>. Perl warns about it, too: `$ perl -wE '$_ = "foo"; s/(foo)/bar \1/; say' \1 better written as $1 at -e line 1. bar foo` [download] We're told that backreference patterns can be used in the substitution by specifying \1, \2 (etc), but it doesn't seem to work. Who told you that?	[reply] [d/l]

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Forgive me, but the working examples do not seem to cover the use of \1 (etc) in the replacement expression.

Unlike sed, we use the \<digit> form in only the left hand side. Anywhere else it's $<digit>.

$ perl -wE '$_ = "foo"; s/(foo)/bar \1/; say'
\1 better written as $1 at -e line 1.
bar foo
[download]

We're told that backreference patterns can be used in the substitution by specifying \1, \2 (etc), but it doesn't seem to work.