You might want to check the results of eval $dumper before you try to use them as a hash reference. Something like

my $hash_ref = eval $dumper;
if ( ! defined $hash_ref ) {
    # You got undef. Handle it as appropriate
} elsif ( 'HASH' eq ref $hash_ref ) {
    # You actually got a hash ref. Handle it.
} else {
    # You got something, but not a hash ref.
    # You don't say this has happened to you, but
    # when troubleshooting, paranoia is justified.
}