The description of the 'a', 'A' & 'Z' templates for pack reads:

    a  A string with arbitrary binary data, will be null padded.
    A  A text (ASCII) string, will be space padded.
    Z  A null-terminated (ASCIZ) string, will be null padded.
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And sure enough:

print length pack '(A2)*', 'fr','ed','x';;
6

print unpack 'C*', pack '(A2)*', 'fr','ed','x';;
102 114 101 100 120 32

print length pack '(a2)*', 'fr','ed','x';;
6

print unpack 'C*', pack '(a2)*', 'fr','ed','x';;
102 114 101 100 120 0

print length pack '(Z2)*', 'fr','ed','x';;
6

print unpack 'C*', pack '(Z2)*', 'fr','ed','x';;
102 0 101 0 120 0  ## Note! the 'r' & 'd' characters have been thrown 
+away? Another bug?
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And the docs for unpack say:

unpack does the reverse of pack: it takes a string and expands it out into a list of values.

But:

printf "'%s'\n", join"'", unpack '(A2)*', 'fredx';;
'fr'ed'x'

printf "'%s'\n", join"'", unpack '(a2)*', 'fredx';;
'fr'ed'x'

printf "'%s'\n", join"'", unpack '(Z2)*', 'fredx';;
'fr'ed'x'
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Shouldn't that last element from unpack ('x') be padded with either space or null?

Has it always been 'wrong'? Is it too late to change it?