Don't localize $@ in Perl < v5.14 as it caused $@ to be clobbered.

See https://metacpan.org/pod/release/RJBS/perl-5.18.2/pod/perl5140delta.pod#Exception-Handling

Fixes #14
Merge pull request #15 from clintongormley/master

Don't localize $@ in Perl < v5.14 as it caused $@ to be clobbered.