You got those links already last time you asked.

Additionally has perlre even a demo similar to your code.

The \g{-1} syntax is interesting, I don't recall that one. When did it come about? (Of course, it's possible it's been around since Perl 4 and I just missed it :) )

Mike

Looks like 5.10 according to perl5100delta:

    Relative backreferences
        A new syntax "\g{N}" or "\gN" where "N" is a decimal integer a
+llows
        a safer form of back-reference notation as well as allowing re
+lative
        backreferences. This should make it easier to generate and emb
+ed
        patterns that contain backreferences. See "Capture buffers" in
        perlre. (Yves Orton)
[download]

The cake is a lie.
The cake is a lie.
The cake is a lie.

Grepping the perldelta* files for \\g lists perl5100delta, so likely the feature was introduced with Perl 5.10.0.

Syntax::Construct to the rescue :-)
map{substr$_->[0],$_->[1]||0,1}[\*||{},3],[[]],[ref qr-1,-,-1],[{}],[sub{}^*ARGV,3]

> When did it come about?

I don't know, but the OP wants $vars which can be used inside Perl code. (which is also documented in multiple ways)

Cheers Rolf
_{(addicted to the Perl Programming Language :)
Wikisyntax for the Monastery}

update

see Re^2: Refer by relative way to regex group (eg. the last one)

Perl 5.9.5 if you want to be picky.

You do not say how your code fails, but if you add use strict; to your example you get

$ perl -Mstrict -Mwarnings -e 'my $word; "foobar" =~ /(oo)(bar)(?{$word=${-1}})/'
Can't use string ("-1") as a SCALAR ref while "strict refs" in use at -e line 1.

Suggestions:

$ perldoc -v '@-'
$ perldoc -v '@+'

Or, under at least Perl 5.10, you could use named captures.

> Suggestions:

sigh...

• $+ aka $LAST_PAREN_MATCH
• $^N aka $LAST_SUBMATCH_RESULT
• @{^CAPTURE}

Cheers Rolf
_{(addicted to the Perl Programming Language :)
Wikisyntax for the Monastery}

update

  DB<29> "ab" =~ /^((.)(.))(?{say $+;say $^N; say "$1 $2 $3\n@{^CAPTUR
+E}"})/
b
ab
ab a b
ab a b
[download]