Re^3: Why is Dumper returning "!!1" for true file test?

I'm not aware of a single perldoc discussing all details, like it's done in MDN for JS.

(Especially as it's mostly internal stuff which could change and the effects are supposed to be DWIM. Like I said most problems arise when converting to other languages, esp. JS)

But you can gather them from various places like perlop or perlglossary .

FWIW and I don't think !!1 used to be dualvar (see Scalar::Util ) prior to 5.36.

Cheers Rolf
_{(addicted to the Perl Programming Language :)

see Wikisyntax for the Monastery}

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Re^4: Why is Dumper returning "!!1" for true file test? by ikegami (Patriarch) on Jan 22, 2024 at 02:53 UTC
FWIW and I don't think !!1 used to be dualvar (see Scalar::Util ) prior to 5.36. It's actually a triplevar, and it has been so at least as far back as 5.6, but probably a lot further back. I don't have 5.6, but here's 5.8.9: `$ 5.8.9/bin/perl -MDevel::Peek -e'Dump(!!1)' SV = PVNV(0x55e2de0d1348) at 0x55e2dd477310 REFCNT = 2147483647 FLAGS = (IOK,NOK,POK,READONLY,pIOK,pNOK,pPOK) IV = 1 NV = 1 PV = 0x55e2de0d2320 "1"\0 CUR = 1 LEN = 8 $ 5.8.9/bin/perl -MDevel::Peek -e'Dump(!!0)' SV = PVNV(0x55aeb71e8320) at 0x55aeb5e05da0 REFCNT = 2147483647 FLAGS = (IOK,NOK,POK,READONLY,pIOK,pNOK,pPOK) IV = 0 NV = 0 PV = 0x55aeb71e8300 ""\0 CUR = 0 LEN = 8` [download]	[reply] [d/l]
Re^5: Why is Dumper returning "!!1" for true file test? by LanX (Saint) on Jan 22, 2024 at 08:27 UTC
In the case of `!!1` it seems to only be just a performance thing, because all values are just `1` , i.e. any later casting would produce the same effect/caching of types. I was confused because prior to this I only heard of `!!0` as dualvar and I'm kinda sure I read it in the perldocs. Cheers Rolf _{(addicted to the Perl Programming Language :) see Wikisyntax for the Monastery}	[reply] [d/l] [select]
Re^6: Why is Dumper returning "!!1" for true file test? by ikegami (Patriarch) on Jan 22, 2024 at 14:23 UTC
In the case of `!!1` it seems to only be just a performance thing I think so. It is slightly different — I can get pPOK+pIOK+pNOK, but I can't also get IOK+NOK+POK — so there could be difference, but I don't know of any.	[reply] [d/l]