Regular expressions with word boundaries no longer working in bash

[Harry Leitzell]

Configuration Information [Automatically generated, do not change]:
Machine: x86_64
OS: linux-gnu
Compiler: gcc
Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='x86_64' 
-DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='x86_64-pc-linux-gnu' 
-DCONF_VENDOR='pc' -DLOCALEDIR='/usr/share/locale' -DPACKAGE='bash' -DSHELL 
-DHAVE_CONFIG_H   -I.  -I../bash -I../bash/include -I../bash/lib   -g -O2 -Wall
uname output: Linux ochof070 2.6.35-24-generic #42-Ubuntu SMP Thu Dec 2 
02:41:37 UTC 2010 x86_64 GNU/Linux
Machine Type: x86_64-pc-linux-gnu

Bash Version: 4.1
Patch Level: 5
Release Status: release

Description:

Doing string matching based on word boundaries no longer works:

$ bash --version
GNU bash, version 3.2.25(1)-release (x86_64-redhat-linux-gnu)
Copyright (C) 2005 Free Software Foundation, Inc.

$ cat test.sh
input="foocombo foo foo bar bar foo bar some stuff foo" # the input
expected="foocombo foo bar some stuff" # this what we expect
for i in ${input[@]}; do
    [[ ! ${old[@]} =~ \\b"${i}"\\b ]] && old=( ${old[@]} $i )
done
for i in ${input[@]}; do
    [[ ! ${new[@]} =~ \b${i}\b ]] && new=( ${new[@]} $i )
done
echo "input:    $input"
echo "expected: $expected"
echo "old code: ${old[*]}"
echo "new code: ${new[*]}"

$ bash test.sh
input:    foocombo foo foo bar bar foo bar some stuff foo
expected: foocombo foo bar some stuff
old code: foocombo foo bar some stuff
new code: foocombo foo foo bar bar foo bar some stuff foo


Repeat-By:

$ bash --version
GNU bash, version 4.1.5(1)-release (x86_64-pc-linux-gnu)
Copyright (C) 2009 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>

This is free software; you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

$ cat test.sh
input="foocombo foo foo bar bar foo bar some stuff foo" # the input
expected="foocombo foo bar some stuff" # this what we expect
for i in ${input[@]}; do
    [[ ! ${old[@]} =~ \\b"${i}"\\b ]] && old=( ${old[@]} $i )
done
for i in ${input[@]}; do
    [[ ! ${new[@]} =~ \b${i}\b ]] && new=( ${new[@]} $i )
done
echo "input:    $input"
echo "expected: $expected"
echo "old code: ${old[*]}"
echo "new code: ${new[*]}"

$ bash test.sh
input:    foocombo foo foo bar bar foo bar some stuff foo
expected: foocombo foo bar some stuff
old code: foocombo foo foo bar bar foo bar some stuff foo
new code: foocombo foo foo bar bar foo bar some stuff foo

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