$ perl -MDevel::Peek -le'$|=1; $x=1; Dump $x; print "x=$x"; Dump $x'
SV = IV(0x816a438) at 0x814f6cc
  REFCNT = 1
  FLAGS = (IOK,pIOK)                 <--- $x is a number
  IV = 1
x=1
SV = PVIV(0x8150b10) at 0x814f6cc
  REFCNT = 1
  FLAGS = (IOK,POK,pIOK,pPOK)        <--- $x is a number and a string
  IV = 1
  PV = 0x81651b8 "1"\0
  CUR = 1
  LEN = 4

##</code><code>##

sub reconstruct_toggle   { ... }
sub reconstruct_with_val { ... }
sub reconstruct_opt_val  { ... }

reconstruct(
   foo => \&reconstruct_toggle,
   bar => \&reconstruct_with_val,
   special => sub { ... },
);