Try this patch, which may only apply cleanly to a recent bleadperl (I'm at patchlevel 13599). Don't forget to run embed.pl after you do. The new -N switch adds this loop around your script:

LINE: while (<DATA>) {

}
[download]

It should doesn't break any of the regression tests. It may break binary compatibility. Use at your own risk. Try this demonstration:

#!/usr/bin/perl -wNp

use strict;

$_ = reverse $_;
__DATA__
citamorhc
si
!sdrawkcab
[download]

Merry Christmas!

--- ~intrpvar.h Tue Dec 11 13:20:28 2001
+++ intrpvar.h Tue Dec 11 13:20:41 2001
@@ -27,6 +27,7 @@
 PERLVARI(Isplitstr, char *, " ")
 PERLVAR(Ipreprocess, bool)
 PERLVAR(Iminus_n, bool)
+PERLVAR(Iminus_N, bool)
 PERLVAR(Iminus_p, bool)
 PERLVAR(Iminus_l, bool)
 PERLVAR(Iminus_a, bool)
--- ~perl.c    Tue Dec 11 13:13:15 2001
+++ perl.c    Wed Dec 12 11:16:14 2001
@@ -1087,6 +1087,7 @@
     case 'M':
     case 'm':
     case 'n':
+    case 'N':
     case 'p':
     case 's':
     case 'u':
@@ -2135,6 +2136,7 @@
 "-l[octal]       enable line ending processing, specifies line termin
+ator",
 "-[mM][-]module  execute `use/no module...' before executing program"
+,
 "-n              assume 'while (<>) { ... }' loop around program",
+"-N              assume 'while (<DATA>) { ... }' loop around program"
+,
 "-p              assume loop like -n but print line also, like sed",
 "-P              run program through C preprocessor before compilatio
+n",
 "-s              enable rudimentary parsing for switches after progra
+mfile",
@@ -2361,6 +2363,11 @@
         Perl_croak(aTHX_ "No space allowed after -%c", *(s-1));
     return s;
     case 'n':
+    PL_minus_n = TRUE;
+    s++;
+    return s;
+    case 'N':
+    PL_minus_N = TRUE;
     PL_minus_n = TRUE;
     s++;
     return s;
--- ~sv.c Tue Dec 11 13:19:16 2001
+++ sv.c Tue Dec 11 13:19:33 2001
@@ -9825,6 +9825,7 @@
     PL_splitstr  = proto_perl->Isplitstr;
     PL_preprocess = proto_perl->Ipreprocess;
     PL_minus_n  = proto_perl->Iminus_n;
+    PL_minus_N  = proto_perl->Iminus_N;
     PL_minus_p  = proto_perl->Iminus_p;
     PL_minus_l  = proto_perl->Iminus_l;
     PL_minus_a  = proto_perl->Iminus_a;
--- ~toke.c Tue Dec 11 13:14:33 2001
+++ toke.c Tue Dec 11 13:32:02 2001
@@ -2435,7 +2435,11 @@
   PL_preambleav = NULL;
      }
      if (PL_minus_n || PL_minus_p) {
-  sv_catpv(PL_linestr, "LINE: while (<>) {");
+  if (PL_minus_N) {
+   sv_catpv(PL_linestr, "LINE: while (<DATA>) {");
+  } else {
+   sv_catpv(PL_linestr, "LINE: while (<>) {");
+  }
   if (PL_minus_l)
       sv_catpv(PL_linestr,"chomp;");
   if (PL_minus_a) {
[download]

Update: (Wed Dec 12 18:20:00 UTC 2001) I missed a couple of spots in perl.c. They've been added to the patch above. They're the first two chunks in that file, and now it works from the command line.