Your data lines are different enough that each type needs its own parser. A hash of coderefs ("dispatch table") will do that nicely,

my $parser = {
    OFF => sub {()},
    SUCCESS => sub {
        local $_ = shift;
        /\((\w*)\)/
    },  # call these in list context!
    ERROR1 => sub {
        local $_ = shift;
        /disk number \((\d+)\) at \((\d+:\d+)\)/;
    },
    WARNING1 => sub {
        local $_ = shift;
        /(\w.*)^/;
    }
};

sub parse_line {
    local $_ = shift;
    my ($key, $data) = split ':', $_, 2;
    $key =~ tr/()//d;
    ($key, $parser->{$key}->($data));
}
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parse_line() should be called in list context, too.