how to investigate "Attempt to reload Readonly/XS.pm aborted"

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Hi there,
I have an error as detailed in the attached tst1.t perl script where the  "use Readonly::XS;" line is failing.I tried to use perl -d debug mode but not working as use line is part of the compile section.
I do not know how to investigate such a problem, so I would appreciate any suggestion.

# ===============================================
# $perl tst1.t
# Attempt to reload Readonly/XS.pm aborted.
# Compilation failed in require at tst1.t line 26.
# BEGIN failed--compilation aborted at tst1.t line 26.
# ===============================================

-- 
Michel Normand

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#!/usr/bin/perl
# TODO: why failure on line 26: "use Readonly::XS;"
# ===============================================
# $perl tst1.t
# Attempt to reload Readonly/XS.pm aborted.
# Compilation failed in require at tst1.t line 26.
# BEGIN failed--compilation aborted at tst1.t line 26.
# ===============================================
# The perl-Readonly-XS package seems correctly installed:
# <mock-chroot>[root@ppc64le /]# rpm -ql perl-Readonly-XS
# /usr/lib64/perl5/vendor_perl/Readonly
# /usr/lib64/perl5/vendor_perl/Readonly/XS.pm
# /usr/lib64/perl5/vendor_perl/auto/Readonly
# /usr/lib64/perl5/vendor_perl/auto/Readonly/XS
# /usr/lib64/perl5/vendor_perl/auto/Readonly/XS/XS.so
# /usr/share/doc/perl-Readonly-XS
# /usr/share/doc/perl-Readonly-XS/Changes
# /usr/share/doc/perl-Readonly-XS/README
# /usr/share/doc/perl-Readonly-XS/t
# /usr/share/doc/perl-Readonly-XS/t/test.t
# /usr/share/man/man3/Readonly::XS.3pm.gz
# ===============================================
use strict;
use warnings;
use Readonly;
use Readonly::XS;
print "\@INC array is " .join(":",@INC) ."\n";

# perl -V
# ...
#   Built under linux
#   Compiled at Feb 25 2014 13:12:26
#   %ENV:
#     PERL5LIB="/usr/lib64/perl5/vendor_perl"
#   @INC:
#     /usr/lib64/perl5/vendor_perl
#     /usr/local/lib64/perl5
#     /usr/local/share/perl5
#     /usr/lib64/perl5/vendor_perl
#     /usr/share/perl5/vendor_perl
#     /usr/lib64/perl5
#     /usr/share/perl5
#     .

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