I have never used Device::BCM2835 but looking at it, it appears to be a complex way of doing something relatively simple. Please do correct me if there is some advantage of using this module that I have overlooked.

The way I set the GPIO pins is:

sub set_gpio {
    my $pin = shift;
    if (open my $val, '>', "/sys/class/gpio/gpio$pin/value") {
        print $val shift;
        close $val;
    } else {
        return "Failed to set pin $pin $!";
    }
    return "SUCCESS";
}
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This way I can set any pin by passing the pin number and the state to the sub. Note that the logic is reversed in that 0 switches on the relay and 1 switches it off again when I have a relay unit attached.