In general you can't know without looking, but in this case it looks like the changes would be fine for 5.6.1. Here is the diff output for the two versions:

16c16
< $VERSION = "0.05";
---
> $VERSION = "0.06";
56,58c56,62
<         delete $self->[0]{$fd}{$io};
<       delete $self->[1]{$fd} unless %{$self->[0]{$fd}};
<       delete $self->[2]{$io};
---
>           delete $self->[0]{$fd}{$io};
>           unless(%{$self->[0]{$fd}}) {
>             # We no longer have any handles for this FD
>             delete $self->[1]{$fd};
>             delete $self->[0]{$fd};
>           }
>           delete $self->[2]{$io};
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