Actually, no need for an API, sort of. There's PerlIO::reverse which lets you just add a layer when opening a file, then use your good ol' Perl API:

open my $fh, "<:reverse", "/etc/passwd";
print for <$fh>;
[download]

Like File::ReadBackwards, but unlike the tac command, PerlIO::reverse only does line-by-line reversing though.