"C comment," you mean.

So it's running the file as a shell script, where the first line runs tcc on the current file and quits.

I always love these things that are really scripts in two (or more) languages. Common is something like this on Windows to make a command script a Perl script. It lets you run your Perl script without having to make sure you had .pl extensions associated. Though, you needed Perl installed, so I never quite got the point.

    @rem = '--*--Perl-*--
    @echo off
    echo Hello from a command script
    perl -x -S %0 %*
    goto endofperl
    @rem ';
    #!perl
    print "Hello from Perl!\n";
    __END__
    :endofperl

By far very less common is to stuff some Perl code in a C# source file. A dev that was way too clever for his own code did this to have a Perl script that would update a C# script file and be self contained. This is a simple example of what it looked like, minus the instant headache anyone got that had to look at the real version:

    #if PerlScript
    $csharp=<<WhyJustWhy;
    #endif
    using System;

    namespace Example
    {
        public static class Program
        {
            static void Main()
            {
                Console.WriteLine("Hello from C#");
            }
        }
    }

    #if PerlScript
    WhyJustWhy
    print("Hello from Perl!")
    __END__
    #endif