Write a Polyglot for Batch, C, Python, Perl, and Java

A polyglot is a program that can be executed in multiple programming languages and will produce the same output. Here's a polyglot code that can be executed in Batch, C, Python, Perl, and Java:

```batch
::'echo "Hello, world!"' & REM Batch

#include <stdio.h>

int main() {
printf("Hello, world!\n");
return 0;
}

print("Hello, world!") # Python

#!/usr/bin/perl
print "Hello, world!\n";

public class HelloWorld {
public static void main(String[] args) {
System.out.println("Hello, world!");
}
}
```

Explanation:
To create a polyglot, we need to understand the syntax and features of each programming language we are using. Let's go through each language in the code:

1. Batch:
In Batch, we use the `echo` command followed by the message we want to print. The `REM` statement is used to include a comment, which is ignored when the code is run in other languages.

2. C:
In C, we include the `<stdio.h>` header for the `printf()` function that allows us to print the message "Hello, world!".

3. Python:
In Python, we use the `print()` function to output the message "Hello, world!".

4. Perl:
In Perl, we use the `print` statement to output the message "Hello, world!". The `#!/usr/bin/perl` line at the beginning of the code is the shebang line, which tells the operating system to interpret the script using Perl.

5. Java:
In Java, we define a `HelloWorld` class with a `main` method that prints the message "Hello, world!" using `System.out.println()` function.

By combining these different code snippets and using appropriate syntax for each language, we have created a polyglot that can be executed in multiple programming languages.