Well, there is some implication in the documentation because it does say: vec EXPR, OFFSET, BITS However, when in doubt, look at the prototype for the routine:

perl -le 'print prototype "CORE::vec"'
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And you'll see that three arguments are required and that they are all coerced into a scalar context (assuming you understand perl's idea of prototypes :-)

As for a work-around, that's easy:

$vec = '';
my ($offset,$bits) = (0, 4);
vec($vec, $offset, $bits) = 1;
$bits = unpack("b*", $vec);
print "$bits\n";
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