Nobody proposed a vec solution yet. Here’s one: 
use feature say;

$_ = "012\xf0ABC\x0f\x00\x01\xff";
say unpack "H*";    #  303132f04142430f0001ff
for (my $i = length; $i--; vec($_, $i, 8) ^= ~0) {}
say unpack "H*";    #  cfcecd0fbebdbcf0fffe00

[download]
Could probably be optimized for 32/64 bits. Whatever. I'm too lazy to benchmark it.

In reply to Re: In-place bitwise NOT? by Grimy
in thread In-place bitwise NOT? by BrowserUk

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