first attempt to put MAIN back, tadzik++ did lot of the early work

src/core/Main.pm

@@ -0,0 +1,112 @@
+my sub MAIN_HELPER($retval = 0) {
+    my $m = callframe(1).my<&MAIN>;
+    return $retval unless $m;
+
+    # We found MAIN, let's process the command line arguments accordingly
+    my sub process-cmd-args (@args is copy) {
+        my (@positional-arguments, %named-arguments);
+        while (@args) {
+            my $passed_value = @args.shift;
+            if $passed_value.substr(0, 1) eq '-'
+            && $passed_value.substr(1, 1) ne '-' {
+                # TODO: warn?
+                @positional-arguments.push: $passed_value;
+            }
+
+            my $negate = False;
+            if $passed_value.substr(0, 2) eq '--' {
+                my $arg = $passed_value.substr(2);
+                if $arg.substr(0, 1) eq '/' {
+                    $arg .= substr(1) ;
+                    $negate = True;
+                }
+
+                if $arg eq '' {
+                    @positional-arguments.push: @args;
+                    last;
+                } elsif $arg.index('=').defined  {
+                    my ($name , $value) = $arg.split('=', 2);
+                    if $negate {
+                        note "Trouble while parsing comand line argument '$arg': Cannot negate something which has an explicit value - ignoring the argument.\n";
+                        next;
+                    }
+                    %named-arguments.push: $name => $value;
+                } else {
+                    %named-arguments.push: $arg => !$negate;
+                }
+            } else {
+                @positional-arguments.push: $passed_value;
+            }
+        }
+
+        return @positional-arguments, %named-arguments
+    }
+
+    my ($p, $n) = process-cmd-args(@*ARGS);
+
+    # TODO: check if a dispatch is possible, and if not,
+    # do some USAGE magic.
+    return $m(|@($p), |%($n));
+
+#    # We could not find the correct main to dispatch to!
+#    # Let's try to run the user defined USAGE sub
+#    my $h = callframe(1).my<&USAGE>;
+#    return $h() if $h;
+#
+#    # We could not find a user defined USAGE sub!
+#    # Let's display a default USAGE message
+#    my @aliases;
+#    my @help-msgs;
+#    for $m.candidates -> $sub {
+#        my $sig = $sub.signature;
+#        my @arguments = ();
+#        for $sig.params -> $param {
+#            my $argument;
+#            if $param.named {
+#                my $param-name = $param.name.substr(1); # Remove $
+#                my %alias = $param.named_names.elems == 2
+#                            ?? get-aliases($param.named_names.hash)
+#                            !! ();
+#
+#                my $long-name = %alias{$param-name} // $param-name;
+#                $argument = "--$long-name"
+#                            ~ ($param.type ~~ Bool
+#                               ?? '' !! "=value-of-$long-name");
+#
+#                if %alias {
+#                    @aliases.push: "  -" ~ %alias.pairs[0].key()
+#                                   ~ " instead of --$long-name"
+#                }
+#            } else {
+#                $argument = $param.name ?? $param.name.substr(1)
+#                                        !! ~$param.constraints;
+#                #TODO: fixme
+#                $argument = 'param' if $argument ~~ /^_block\d+$/;
+#
+#                if $param.slurpy {
+#                    $argument ~= " [more [...]]";
+#                }
+#            }
+#            $argument = "[$argument]" if $param.optional;
+#            if $param.named {
+#                @arguments.unshift($argument);
+#            } else {
+#                @arguments.push($argument);
+#            }
+#        }
+#        @help-msgs.push(
+#            ($*PROGRAM_NAME eq '-e' ?? "-e '...'" !! $*PROGRAM_NAME)
+#            ~ ' ' ~ @arguments.join(' ');
+#        );
+#    }
+#    my $msg = "Usage:\n" ~ @help-msgs.join("\nor\n");
+#    if @aliases {
+#        $msg ~= "\nYou can use\n" ~ @aliases.join("\n")
+#    }
+#    if @*ARGS ~~ ['--help'] {
+#        $*OUT.say($msg);
+#    } else {
+#        $*ERR.say($msg);
+#        exit 29; #TODO: Better return value
+#    }
+}

tools/build/Makefile.in

@@ -197,6 +197,7 @@ CORE_SOURCES = \
   src/core/Grammar.pm \
   src/core/Regex.pm \
   src/core/CallFrame.pm \
+  src/core/Main.pm \
   src/core/tai-utc.pm \
   src/core/Instant.pm \
   src/core/Duration.pm \