And is confusing because you need to mentally negate it again, while !! is a common idiom.

But the performance question occurred to me already I kind of expected constant folding to happen.

update

ha, indeed! :)

  DB<5> p B::Deparse->new()->coderef2text( sub{!!1} )
{
    use feature ... ; # shortened
    !0;
}
  DB<6> p B::Deparse->new()->coderef2text( sub{!!0} )
{
    use feature ... ; # yadda
    !1;
}
  DB<7> p $]
5.038002
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