Additionally implement a numerical version, ==:u

Author: leonerd

lib/B/Op_private.pm

@@ -1681,6 +1681,15 @@ PP(pp_eq)
     SV *right = PL_stack_sp[0];
     SV *left  = PL_stack_sp[-1];
 
+    if(UNLIKELY(PL_op->op_private & OPpEQ_UNDEF)) {
+        bool lundef = !SvOK(left), rundef = !SvOK(right);
+
+        if(lundef || rundef) {
+            rpp_replace_2_IMM_NN(boolSV(lundef && rundef));
+            return NORMAL;
+        }
+    }
+
     U32 flags_and = SvFLAGS(left) & SvFLAGS(right);
     U32 flags_or  = SvFLAGS(left) | SvFLAGS(right);
 

opcode.h

@@ -920,9 +920,9 @@ addbits('emptyavhv',
   # 4       OPpTARGET_MY
 );
 
-addbits('seq',
+addbits($_,
     7 => qw(OPpEQ_UNDEF UNDEF),
-);
+) for qw( eq seq );
 
 addbits('argdefelem',
     7 => qw(OPpARG_IF_UNDEF  IF_UNDEF),

pp_hot.c

@@ -10,6 +10,8 @@ BEGIN {
 }
 
 ### PPC0030-style `equ` operator
+#   does not test the numerical version because there are still discussions
+#   about its spelling; `===` is considered problematic.
 
 # equ behaves like eq on defined strings
 ok("abc" equ "abc",      'equ on identical values');
@@ -42,6 +44,11 @@ ok("abc" eq:u "abc",      'eq:u on identical values');
 ok("" eq:u "",            'eq:u on empty/empty');
 ok(not("abc" eq:u "def"), 'eq:u on different values');
 
+# ==:u behaves like == on defined numbers
+ok(123 ==:u 123,      '==:u on identical values');
+ok(0 ==:u 0,          '==:u on zero/zero');
+ok(not(123 ==:u 456), '==:u on different values');
+
 # eq:u treats undef as distinct, equal to itself, with no warnings
 {
     my $warnings = 0;
@@ -53,6 +60,17 @@ ok(not("abc" eq:u "def"), 'eq:u on different values');
     is($warnings, 0, 'no warnings were produced by use of undef');
 }
 
+# ==:u treats undef as distinct, equal to itself, with no warnings
+{
+    my $warnings = 0;
+    local $SIG{__WARN__} = sub { $warnings++; };
+
+    ok(undef ==:u undef,   'eq:u on undef/undef');
+    ok(not(undef ==:u 0), 'eq:u on undef/zero');
+
+    is($warnings, 0, 'no warnings were produced by use of undef');
+}
+
 # performs GETMAGIC
 {
     "abc" =~ m/(\d+)/;