Avoid s///r to support pre-5.14 Perls

I got some error reports from CPANTesters, like this:
http://cpantesters.org/cpan/report/56678a16-de66-11e2-bc9b-6c1b697f9654

Signed-off-by: Gustavo L. de M. Chaves <gnustavo@cpan.org>
v0.044

  [Fixes]

  - Version 0.043 used the s///r operator, which was implemented on
    Perl 5.14. This version refactors it to avoid the operator and
    keep compatibility with Perl 5.10.