$INPUT->param("titles")
returns a list. You can't index a list, but you can slice it.
($INPUT->param("titles"))[5]

Sure you can - perldata uses subscript instead of index:

A common way to access an array or a hash is one scalar element at a time. You can also subscript a list to get a single element from it.

You can't subscript a function call, though, only its results - that's why the expression must go in parens. But you are right in that you can also slice a list :-)

_($_=" "x(1<<5)."?\n".q·/)Oo.  G°\        /
                              /\_¯/(q    /
----------------------------  \__(m.====·.(_("always off the crowd"))."·
");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}

A common way to access an array or a hash is one scalar element at a time. You can also subscript a list to get a single element from it.

And by doing so, you get a list slice. A single-index slice is still a slice. The difference between a slice and indexing is the context in which the index expression is evaluated.

my @indexes = (3);

my @array = (0,1,2,3,4);
print($array[@indexes], "\n");  # 1 => index
print(@array[@indexes], "\n");  # 3 => slice

print((0,1,2,3,4,5)[@indexes], "\n");  # 3 => slice
[download]

There's no native syntax to index a list.

The difference between a slice and indexing is the context in which the index expression is evaluated.

I see. That's why this sentence is found under Slices in perldata. Learnt something new today, thank you.

update: looks like a statement like this one deserves downvoting for some. *shrug*

--shmem

_($_=" "x(1<<5)."?\n".q·/)Oo.  G°\        /
                              /\_¯/(q    /
----------------------------  \__(m.====·.(_("always off the crowd"))."·
");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}