Please, send the output of:

/bin/sh --version
ls -l /bin | grep sh

I can not repeat on CentOS 6.4:

[root@centos openxs]# rpm -q -a | grep -i percona
Percona-Server-shared-compat-5.5.32-rel31.0.549.rhel6.x86_64
Percona-Server-55-debuginfo-5.5.32-rel31.0.549.rhel6.x86_64
percona-release-0.0-1.x86_64
[root@centos openxs]# yum -y install Percona-Server-server-55 Percona-Server-client-55 Percona-Server-devel-55 Percona-Server-shared-55
Loaded plugins: fastestmirror, presto
Loading mirror speeds from cached hostfile
 * base: ftp.tlk-l.net
 * epel: ftp.tlk-l.net
 * extras: ftp.tlk-l.net
 * rpmforge: ftp.colocall.net
 * updates: ftp.tlk-l.net
Setting up Install Process
Resolving Dependencies
--> Running transaction check
---> Package Percona-Server-client-55.x86_64 0:5.5.32-rel31.0.549.rhel6 will be installed
---> Package Percona-Server-devel-55.x86_64 0:5.5.32-rel31.0.549.rhel6 will be installed
---> Package Percona-Server-server-55.x86_64 0:5.5.32-rel31.0.549.rhel6 will be installed
---> Package Percona-Server-shared-55.x86_64 0:5.5.32-rel31.0.549.rhel6 will be installed
--> Finished Dependency Resolution

Dependencies Resolved

================================================================================
 Package                    Arch     Version                    Repository
                                                                           Size
================================================================================
Installing:
 Percona-Server-client-55   x86_64   5.5.32-rel31.0.549.rhel6   percona   6.3 M
 Percona-Server-devel-55    x86_64   5.5.32-rel31.0.549.rhel6   percona   2.8 M
 Percona-Server-server-55   x86_64   5.5.32-rel31.0.549.rhel6   percona    15 M
 Percona-Server-shared-55   x86_64   5.5.32-rel31.0.549.rhel6   percona   647 k

Transaction Summary
================================================================================
Install       4 Package(s)

Total download size: 25 M
Installed size: 104 M
Downloading Packages:
Setting up and reading Presto delta metadata
Processing delta metadata
Package(s) data still to download: 25 M
(1/4): Percona-Server-client-55-5.5.32-rel31.0.549.rhel6 | 6.3 MB     00:14
(2/4): Percona-Server-devel-55-5.5.32-rel31.0.549.rhel6. | 2.8 MB     00:05
(3/4): Percona-Server-server-55-5.5.32-rel31.0.549.rhel6 |  15 MB     00:29
(4/4): Percona-Server-shared-55-5.5.32-rel31.0.549.rhel6 | 647 kB     00:01
--------------------------------------------------------------------------------
Total                                           479 kB/s |  25 MB     00:53
Running rpm_check_debug
Running Transaction Test
Transaction Test Succeeded
Running Transaction
  Installing : Percona-Server-shared-55-5.5.32-rel31.0.549.rhel6.x86_64     1/4
  Installing : Percona-Server-client-55-5.5.32-rel31.0.549.rhel6.x86_64     2/4
  Installing : Percona-Server-server-55-5.5.32-rel31.0.549.rhel6.x86_64     3/4
ls: cannot access /var/lib/mysql/*.err: No such file or directory
ls: cannot access /var/lib/mysql/*.err: No such file or directory
Percona Server is distributed with several useful UDF (User Defined Function) from Maatkit.
Run the following commands to create these functions:
mysql -e "CREATE FUNCTION fnv1a_64 RETURNS INTEGER SONAME 'libfnv1a_udf.so'"
mysql -e "CREATE FUNCTION fnv_64 RETURNS INTEGER SONAME 'libfnv_udf.so'"
mysql -e "CREATE FUNCTION murmur_hash RETURNS INTEGER SONAME 'libmurmur_udf.so'"
See http://code.google.com/p/maatkit/source/browse/trunk/udf for more details
  Installing : Percona-Server-devel-55-5.5.32-rel31.0.549.rhel6.x86_64      4/4
  Verifying  : Percona-Server-server-55-5.5.32-rel31.0.549.rhel6.x86_64     1/4
  Verifying  : Percona-Server-devel-55-5.5.32-rel31.0.549.rhel6.x86_64      2/4
  Verifying  : Percona-Server-shared-55-5.5.32-rel31.0.549.rhel6.x86_64     3/4
  Verifying  : Percona-Server-client-55-5.5.32-rel31.0.549.rhel6.x86_64     4/4

Installed:
  Percona-Server-client-55.x86_64 0:5.5.32-rel31.0.549.rhel6
  Percona-Server-devel-55.x86_64 0:5.5.32-rel31.0.549.rhel6
  Percona-Server-server-55.x86_64 0:5.5.32-rel31.0.549.rhel6
  Percona-Server-shared-55.x86_64 0:5.5.32-rel31.0.549.rhel6

Complete!

Here is the output in my case:

[root@centos openxs]# /bin/sh --version
GNU bash, version 4.1.2(1)-release (x86_64-redhat-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.

[root@centos openxs]# ls -l /bin | grep sh
-rwxr-xr-x. 1 root root  903272 Feb 21 23:09 bash
-rwxr-xr-x. 1 root root   15440 Jun 25 17:23 cgsnapshot
-rwxr-xr-x. 1 root root  106216 Oct 17  2012 dash
lrwxrwxrwx. 1 root root       4 May 28 19:38 sh -> bash


Maybe you have some other shell (that does not understand script syntax) installed as /bin/sh.