Perl

[Prentitious]

I know that Java is based on this principle:
"Java should allow the same program to be executed on multiple operating systems."

I know that C++ does not comply with this statement. But does Perl?

[Deerpark]

No.
Java accomplish being cross platform by running its code in a virtual machine called the JVM. In order for Java to run on a given platform a platform compatible JVM must be written.
Only other mainstream programming framework I know that uses a VM is the .NET framework.

[Prentitious]

I think that Perl is highly cross-platform though, because you can use GUI interfaces that are made in Windows, exactly the same on a Unix machine...

[ghostdog74]

I think that Perl is highly cross-platform though, because you can use GUI interfaces that are made in Windows, exactly the same on a Unix machine...

what one needs is the "interpreter". You can write perl scripts in windows, and bring it to run in *nix and run it with little/minimal changes. Others like Python,Java,Ruby,Php etc are all cross platform, all thanks to the interpreter.