diff --git a/src/create_cmdidxs.pl b/src/create_cmdidxs.pl
new file mode 100644
index 0000000..ff8dcc3
--- /dev/null
+++ b/src/create_cmdidxs.pl
@@ -0,0 +1,74 @@
+#!/usr/bin/perl -w
+#
+# This script generates the tables cmdidxs1[] and cmdidxs2[][] which,
+# given a Ex command, determine the first value to probe to find
+# a matching command in cmdnames[] based on the first character
+# and the first 2 characters of the command.
+# This is used to speed up lookup in cmdnames[].
+#
+# Script should be run every time new Ex commands are added in Vim,
+# from the src/vim directory, since it reads commands from "ex_cmds.h".
+
+# Find the list of Vim commands from cmdnames[] table in ex_cmds.h
+my @cmds;
+my @skipped;
+open(IN, "< ex_cmds.h") or die "can't open ex_cmds.h: $!\n";
+while (<IN>) {
+  if (/^EX\(CMD_\S*,\s*"([a-z][^"]*)"/) {
+    push (@cmds, $1);
+  } elsif (/^EX\(CMD_/) {
+    push (@skipped, $1);
+  }
+}
+
+my %cmdidxs1;
+my %cmdidxs2;
+
+for (my $i = $#cmds; $i >= 0; --$i) {
+  my $cmd = $cmds[$i];
+  my $c1 = substr($cmd, 0, 1); # First character of command.
+
+  $cmdidxs1{$c1} = $i;
+
+  if (length($cmd) > 1) {
+    my $c2 = substr($cmd, 1, 1); # Second character of command.
+    $cmdidxs2{$c1}{$c2} = $i if (('a' lt $c2) and ($c2 lt 'z'));
+  }
+}
+
+print "/* Beginning of automatically generated code by create_cmdidxs.pl\n",
+      " *\n",
+      " * Table giving the index of the first command in cmdnames[] to lookup\n",
+      " * based on the first letter of a command.\n",
+      " */\n",
+      "static const unsigned short cmdidxs1[26] =\n{\n",
+      join(",\n", map("  /* $_ */ $cmdidxs1{$_}", ('a' .. 'z'))),
+      "\n};\n",
+      "\n",
+      "/*\n",
+      " * Table giving the index of the first command in cmdnames[] to lookup\n",
+      " * based on the first 2 letters of a command.\n",
+      " * Values in cmdidxs2[c1][c2] are relative to cmdidxs1[c1] so that they\n",
+      " * fit in a byte.\n",
+      " */\n",
+      "static const unsigned char cmdidxs2[26][26] =\n",
+      "{ /*         a   b   c   d   e   f   g   h   i   j   k   l   m   n   o   p   q   r   s   t   u   v   w   x   y   z */\n";
+for my $c1 ('a' .. 'z') {
+  print "  /* $c1 */ {";
+  for my $c2 ('a' .. 'z') {
+    if (exists $cmdidxs2{$c1}{$c2}) {
+      printf "%3d,", $cmdidxs2{$c1}{$c2} - $cmdidxs1{$c1};
+    } else {
+      printf "  0,";
+    }
+  }
+  print " }";
+  print "," unless ($c1 eq 'z');
+  print "\n";
+}
+print "};\n",
+      "\n",
+      "static int command_count = ", $#cmds + $#skipped + 2 , ";\n",
+      "\n",
+      "/* End of automatically generated code by create_cmdidxs.pl */\n";
+