use Config     qw( %Config );
use List::Util qw( max );

my $max = max( ~0+1, eval( $Config{ nv_overflows_integers_at } ) );

##</code><code>##

[+/-]1._____..._____ * 2**____

##</code><code>##

     __52 bits__
    /           \
  1.00000...00000  * 2**53    Large power of two
+ 1.00000...00000  * 2**0     1
--------------------------
  1.00000...00000  * 2**53
+ 0.00000...000001 * 2**53    Normalized exponents
--------------------------
  1.00000...000001 * 2**53    But we have limited number of bits
--------------------------
  1.00000...00000  * 2**53    Original large power of two

##</code><code>##

$ perl -MB=svref_2object,SVf_IVisUV,SVf_NOK -e'
   $i = 0;
   $sv = svref_2object(\$i);
   print $sv->FLAGS & SVf_NOK    ? "NV\n"   # Float
      :  $sv->FLAGS & SVf_IVisUV ? "UV\n"   # Unsigned int
      :                            "IV\n";  # Signed int
'
IV

##</code><code>##

$ perl -MConfig -MB=svref_2object,SVf_IVisUV,SVf_NOK -e'
   $i = hex("7F".("FF"x($Config{ivsize}-2))."FD");
   $sv = svref_2object(\$i);
   for (1..4) {
      ++$i;
      printf $sv->FLAGS & SVf_NOK    ? "NV %.0f\n"
         :   $sv->FLAGS & SVf_IVisUV ? "UV %u\n"
         :                             "IV %d\n", $i;
   }
'
IV 2147483646
IV 2147483647            <-- 2**31 - 1  Largest IV
UV 2147483648
UV 2147483649

##</code><code>##

IV 9223372036854775806
IV 9223372036854775807   <-- 2**63 - 1  Largest IV
UV 9223372036854775808
UV 9223372036854775809

##</code><code>##

$ perl -V:[in]vsize
ivsize='4';   # 32-bit integers
nvsize='8';   # 64-bit floats

##</code><code>##

$ perl -V:[in]vsize
ivsize='8';   # 64-bit integers
nvsize='8';   # 64-bit floats

##</code><code>##

$ perl -MConfig -MB=svref_2object,SVf_IVisUV,SVf_NOK -e'
   $i = eval($Config{nv_overflows_integers_at}) - 3;
   $sv = svref_2object(\$i);
   for (1..4) {
      ++$i;
      printf $sv->FLAGS & SVf_NOK    ? "NV %.0f\n"
         :   $sv->FLAGS & SVf_IVisUV ? "UV %u\n"
         :                             "IV %d\n", $i;
   }
'
NV 9007199254740990
NV 9007199254740991                 Precision required as a float:
NV 9007199254740992  <-- 2**53      1 bit
NV 9007199254740992  <-- 2**53 + 1  54 bits, but only 53 are available

##</code><code>##

$ perl -MConfig -MB=svref_2object,SVf_IVisUV,SVf_NOK -e'
   $i = hex(("FF"x($Config{ivsize}-1))."FD");
   $sv = svref_2object(\$i);
   for (1..4) {
      ++$i;
      printf $sv->FLAGS & SVf_NOK    ? "NV %.0f\n"
         :   $sv->FLAGS & SVf_IVisUV ? "UV %u\n"
         :                             "IV %d\n", $i;
   }
'
UV 18446744073709551614
UV 18446744073709551615  <-- 2**64 - 1  Largest UV
NV 18446744073709551616  <-- 2**64      1 bit of precision required
NV 18446744073709551616  <-- 2**64 + 1  65, but only 53 are available