Re^4: Why is Dumper returning "!!1" for true file test?

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
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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]