!!! Supplementary for future readers of this comment thread !!!

The pragma autodie also spots this problem!

So....

    use strict;
    use warnings;
    use autodie;

    our $config;
    $config->{file_paht} = "somefile";

    open my $fh, '<', $config->{file_path};

Will throw an exception at open(). NB. Bizarrely the error is Use of uninitialized value $file in sprintf... but hey the problem is still caught :)