I would go a step further and make an accessor for %TZMap

sub TZMap {
    my $self = shift;
    if (@_) {
        $self->{TZMap} = {@_}
    }
    return $self->{TZMap};
}
[download]

And then later

sub check_timezones {
    # same as ...

    print Dumper { $self->TZMap() };

    # same as ...
}
[download]

Furthermore, I'd look into object construction modules out on CPAN. I personally recommend Moose