How to tell apart numeric scalars and string scalars in Perl?

Question

Perl usually converts numeric to string values and vice versa transparently. Yet there must be something which allows e.g. Data::Dumper to discriminate between

Answer 1

It is more complicated. Perl changes the internal representation of a variable depending on the context the variable is used in:

perl -MDevel::Peek -e '
    $x = 1;    print Dump $x;
    $x eq "a"; print Dump $x;
    $x .= q(); print Dump $x;
'
SV = IV(0x794c68) at 0x794c78
  REFCNT = 1
  FLAGS = (IOK,pIOK)
  IV = 1
SV = PVIV(0x7800b8) at 0x794c78
  REFCNT = 1
  FLAGS = (IOK,POK,pIOK,pPOK)
  IV = 1
  PV = 0x785320 "1"\0
  CUR = 1
  LEN = 16
SV = PVIV(0x7800b8) at 0x794c78
  REFCNT = 1
  FLAGS = (POK,pPOK)
  IV = 1
  PV = 0x785320 "1"\0
  CUR = 1
  LEN = 16