Inconsistent/missing warnings with pack

[Tux]

All tested with perl-5.30.0

1. pack does not warn when not enough arguments are passed:

$ perl -wE'use strict; $a = pack "s>s>s> s>", 1, 2, 3'

2. pack does warn when passing explicit undef:

$ perl -wE'use strict; $a = pack "s>s>s> s>", 1, 2, 3, undef'
Use of uninitialized value in pack at -e line 1.

So, what is the difference? Why does the first not warn?

Likewise
3. pack does not warn when not enough arguments in array:

$ perl -wE'use strict; my @v = (1..3); $a = pack "s>s>s> s>", @v'

4. pack does not warn when too many arguments in array:

$ perl -wE'use strict; my @v = (1..5); $a = pack "s>s>s> s>", @v'

5. pack does warn when array has explicit undef:

$ perl -wE'use strict; my @v = (1..3,undef); $a = pack "s>s>s> s>", @v'
Use of uninitialized value $v[3] in pack at -e line 1.

It took my hours to find why

 my @v = unpack "..... s>s>s>" => $input;

had three trailing zeroes where the value was generated in another process passing it through a pipe

 $input = pack "..... s>s>s>", @values;

and @values was missing the three last values