diff -up Text-BibTeX-0.70/lib/Text/BibTeX/Value.pm.orig Text-BibTeX-0.70/lib/Text/BibTeX/Value.pm
--- Text-BibTeX-0.70/lib/Text/BibTeX/Value.pm.orig	2015-04-30 10:13:15.785918161 +0200
+++ Text-BibTeX-0.70/lib/Text/BibTeX/Value.pm	2015-04-30 10:21:35.467626175 +0200
@@ -18,7 +18,6 @@
 package Text::BibTeX::Value;
 
 use strict;
-use UNIVERSAL 'isa';
 use Carp;
 
 use vars qw'$VERSION';
@@ -206,7 +205,7 @@ sub new
          if ref $sval eq 'ARRAY' && @$sval == 2;
       croak "simple value is neither a two-element array ref " .
             "nor a Text::BibTeX::SimpleValue object"
-         unless isa ($sval, 'Text::BibTeX::SimpleValue');
+         unless ref $sval eq 'Text::BibTeX::SimpleValue';
       push (@$self, $sval);
    }