You're almost there.

As you say, unpack takes a string as its argument. If you supply an integer, then Perl quietly converts it to a (human readable) string for you, just as it does when do print 0; It 'ascii-ises' the number. In C terms, Perl does an itoa() on it.

Conversely, when you pack the number, the string returned contains the machine readable, binary representation embedded within a string. In C terms, it is like doing:

int i = 0;

printf( "%s", (char*)&i );
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