% perl -wE 'stat("nonexistent"); $e = $!; say $e; say $e+0'
No such file or directory
2

##</code><code>##

% perl -MDevel::Peek -we '
  $val = ""; Dump($val);
  $val ||= 0; Dump($val);
  $val =~ /^\d+$/; Dump($val);
' 2>&1 | grep V
SV = PV(0x561cd5e52da0) at 0x561cd5e7a028
  PV = 0x561cd5e9b150 ""\0
SV = PVIV(0x561cd5e74e60) at 0x561cd5e7a028
  IV = 0
  PV = 0
SV = PVIV(0x561cd5e74e60) at 0x561cd5e7a028
  IV = 0
  PV = 0x561cd5e7b6a0 "0"\0