R help - Jan 2010 - unexpected behaviour of R-2.10.1 regular expression in UTF-8 locale

Dear R-helpers,

I have encountered the following unexpected behaviour of R-2.10.1, but not
R-2.9.0,
on both RHEL 4 and Ubuntu Karmic (precompiled via synaptic or built from
source).

I have a character vector from which I want to extract a certain pattern
that is surrounded
by junk as in:
> nn <- sprintf("junk_%02d_junk", 1:2)
> nn
[1] "junk_01_junk" "junk_02_junk"
> sub("^.*([[:digit:]]{2}).*$", "\\1", nn)
[1] "nk" "nk"
# oops? however:
> sub("^.*([[:digit:]]{2}).*$", "\\1", nn, perl = TRUE)
[1] "01" "02"

# as expected, and also
> Sys.setlocale("LC_ALL", "C")
[1]
"LC_CTYPE=C;LC_NUMERIC=C;LC_TIME=C;LC_COLLATE=C;LC_MONETARY=C;LC_MESSAGES=en_US.UTF-8;LC_PAPER=en_US.UTF-8;LC_NAME=C;LC_ADDRESS=C;LC_TELEPHONE=C;LC_MEASUREMENT=en_US.UTF-8;LC_IDENTIFICATION=C"
> sub("^.*([[:digit:]]{2}).*$", "\\1", nn)
[1] "01" "02"

Is there something wrong with my regex syntax or am I missing something
else?
Obviously I have at least two workarounds but I'd like to report this since
it is
breaking code that used to run in R-2.9.0.

Thanks in advance for any help or insight,

 - axel



$ R --vanilla

R version 2.10.1 (2009-12-14)
Copyright (C) 2009 The R Foundation for Statistical Computing
ISBN 3-900051-07-0

R is free software and comes with ABSOLUTELY NO WARRANTY.
You are welcome to redistribute it under certain conditions.
Type 'license()' or 'licence()' for distribution details.

  Natural language support but running in an English locale

R is a collaborative project with many contributors.
Type 'contributors()' for more information and
'citation()' on how to cite R or R packages in publications.

Type 'demo()' for some demos, 'help()' for on-line help, or
'help.start()' for an HTML browser interface to help.
Type 'q()' to quit R.
> sessionInfo()
R version 2.10.1 (2009-12-14)
x86_64-pc-linux-gnu

locale:
 [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C
 [3] LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8
 [5] LC_MONETARY=C              LC_MESSAGES=en_US.UTF-8
 [7] LC_PAPER=en_US.UTF-8       LC_NAME=C
 [9] LC_ADDRESS=C               LC_TELEPHONE=C
[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base



Axel Klenk
Research Informatician
Actelion Pharmaceuticals Ltd / Gewerbestrasse 16 / CH-4123 Allschwil /
Switzerland



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