Found.

diff --git a/gpt b/gpt
new file mode 100755 (executable)
index 0000000..7fca9c5
--- /dev/null
+++ b/gpt
@@ -0,0 +1,154 @@
+#!/usr/bin/perl
+
+package GenericPrepTemplate;
+
+#BEGIN {
+#    use Exporter ();
+#    use vars qw($VERSION @ISA @EXPORT @EXPORT_OK %EXPORT_TAGS);
+#    $VERSION= 1.00;
+#    @ISA= qw(Exporter);
+#    @EXPORT= qw(&process_input);
+#    %EXPORT_TAGS= ();
+#    @EXPORT_OK= qw();
+#}
+#use vars @EXPORT_OK;
+#use vars qw($fh);
+
+use IO::Handle;
+use IO::File;
+
+open DEBUG, ">&4";
+
+$fh= new IO::Handle;
+$fh->fdopen(fileno(STDIN),'r') or die;
+process_fh($fh,'<standard input>');
+close STDOUT or die "gpt: close stdout: $!\n";
+exit 0;
+
+sub err ($) { die "gpt: $fn:$lno: $_[0]\n"; }
+
+sub add_perl ($) {
+    my ($str) = @_;
+    if (@oplist>1) { $substr.= $str; }
+    else { $expr.= $str; }
+}
+
+sub add_text ($) {
+    my ($str) = @_;
+    if (@oplist) { $substr.=$str; }
+    else { output($str); }
+}
+               
+sub process_input () {
+    my ($esc,$top,$want,$fh,$value);
+    while (length $l) {
+       print DEBUG "L $fn:$lno:",join('',@oplist),
+                   ":`$l' e\`$expr' s\`$substr'\n";
+       if (@oplist & 1) { # scanning perl
+           if ($l =~ m/(.)\@\@/m || $l =~ m/^()\@\@/m) {
+               ($to,$op,$esc,$l) = ($`,$1,$&,$');
+               add_perl($to);
+               if ($op =~ m/[ 0-9a-zA-Z_\;\)\}]/ || $op eq '') {
+                   $top= pop @oplist;
+                   if (!@oplist) {
+                       # And evaluate.
+                       $expr.= $op;
+                       $@='';
+                       print DEBUG "E $fn:$lno:e\`$expr'\n";
+                       $value= do {
+                           package main;
+                           eval $GenericPrepTemplate::expr;
+                       };
+                       if (length $@) {
+                           chomp $@; err("error: $@");
+                       }
+                       print DEBUG "E $fn:$lno:v\`$value'\n";
+                       if ($top eq '<') {
+                           $fh= new IO::File $value,'r'
+                               or err("cannot open file \`$value': $!");
+                           process_fh($fh,$value);
+                           $fh->close;
+                       } elsif ($top ne '-') {
+                           output($value);
+                       }
+                       $expr='';
+                   } else {
+                       $substr.= $esc;
+                   }
+               } elsif ($op =~ m/[\(\{]/) {
+                   if (@oplist>1) { $substr.= $esc; }
+                   push @oplist, $op;
+               } else {
+                   err("bad escape sequence $op\@\@ in perl part");
+               }
+           } else {
+               add_perl($l);
+               $l= '';
+           }
+       } else { # scanning text
+           if ($l =~ m/\@\@(.|\n)/) {
+               ($to,$op,$esc,$l) = ($`,$1,$&,$');
+               add_text($to);
+               if ($op =~ m/[-< \$]/) {
+                   $substr.= $esc if @oplist;
+                   push @oplist, $op;
+               } elsif ($op =~ m/[\)\}]/) {
+                   err("unmatched closing \@\@$op") unless @oplist;
+                   my ($want);
+                   $want= $oplist[$#oplist] eq '(' ? ')' : '}';
+                   err("found \@\@$op but wanted \@\@$want")
+                       unless $want eq $op;
+                   pop @oplist;
+                   if (@oplist==1) {
+                       # Just finished a substr.
+                       $substri++;
+                       $substrs[$substri]= $substr;
+                       print DEBUG "S $fn:$lno:S$substri\`$substr'\n";
+                       $expr.= ' GenericPrepTemplate::output(' if $op eq '}';
+                       $expr.= " GenericPrepTemplate::process_i($substri) ";
+                       $expr.= " );\n" if $op eq '}';
+                       $substr='';
+                   } else {
+                       $substr.= $esc;
+                   }
+               } else {
+                   err("bad escape sequence \@\@$op in text part");
+               }
+           } else {
+               add_text($l);
+               $l= '';
+           }
+       }
+    }
+}
+
+sub process_fh ($$) {
+    local ($fh,$fn) = @_;
+    local ($l,$lno, @oplist,$substr,$expr,$to,$op);
+
+    while (defined ($l= $fh->getline)) {
+       next if $l =~ m,^\#\! ?/\S+/gpt\b, && $.==1;
+       $lno= $.;
+       process_input();
+    }
+    die "gpt: $fn: read error: $!" if $fh->error;
+}
+
+sub output ($) {
+    if (defined $outbuf) {
+       print DEBUG "O \`$outbuf'+\`$_[0]'\n";
+       $outbuf.= $_[0];
+    } else {
+       print DEBUG "O w\`$_[0]'\n";
+       print STDOUT $_[0] or err("write stdout: $!");
+    }
+}
+
+sub process_i ($) {
+    my ($i) = @_;
+    local ($l,$fn,$lno) = ($substrs[$i], "$fn<sub#$i>", '');
+    local ($outbuf, @oplist,$substr,$expr,$to,$op);
+    $outbuf='';
+    process_input();
+    return $outbuf;
+}