That's definitely a strange behavior, here's a fairly short way to reproduce it:

$ perl -wMstrict -MDevel::Peek -le 'my $x="11a"; $SIG{__WARN__}
       = sub{$x="99"}; print "num: ",$x+0,", str: $x"; Dump($x)'

num: 11, str: 99
SV = PVNV(0x59efe266a440) at 0x59efe2692648
  REFCNT = 2
  FLAGS = (POK,IsCOW,pIOK,pNOK,pPOK)
  IV = 11
  NV = 11
  PV = 0x59efe26d3ae0 "99"\0
  CUR = 2
  LEN = 10
  COW_REFCNT = 1

[download]

My guess is it's the signal handler: I am guessing it gets called during the $n+0 operation which produces the warning, and so an assignment to the string component of the variable during that operation leaves it in a state where the string and numeric components differ. So it's very similar to:

$ perl -wMstrict -MDevel::Peek -MScalar::Util=dualvar
                 -e 'my $x=dualvar(11,"99"); Dump($x)'

[download]

I'm not sure if this is worth a bug report or not.

In reply to Re^4: Converting to number doesn't always work... by haukex
in thread Converting to number doesn't always work... by harangzsolt33

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