Actually, I do use windows and do know a little about what's going on.

The difference is that on *nix, you're creating a process tree like this:

yourshell
  perl bugSTDOUT.pl
     perl bugSTDOUTb.pl
        perl bugSTDOUTc.pl
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Under windows it looks like this:

cmd.exe
  perl bugSTDOUT.pl           *
    cmd.exe                   *
      perl bugSTDOUTb.pl      *
        cmd.exe
          perl bugSTDOUTc.pl
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I could go on to mention the pipe instance that is shared between the three marked processes; and the need to explicitly set a flag on a CreateProcess call to cause spawned process to inherit handles from its parent, but you likely wouldn't be interested.

If you more exactly emulate the *nix handling of the situation, by suppressing the creation of those intermediary shell processes with their associated virtual consoles, thus:

C:\test>type bug*

bugSTDOUT.pl

#!/usr/bin/perl
print STDOUT "Running bugSTDOUTb.pl with backticks\n";
print STDOUT "stdout from bugSTDOUTb.pl=" . `$^X bugSTDOUTb.pl` . "\n"
+;

bugSTDOUTb.pl

#!/usr/bin/perl
print STDOUT "Running bugSTDOUTc.pl with system()\n";
system( $^X, 'bugSTDOUTc.pl' );
print STDOUT "$0 done\n";

bugSTDOUTc.pl

#!/usr/bin/perl
print STDOUT "Hello world!\n";
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You get the behaviour you are seeking:

C:\test>bugSTDOUT.pl
Running bugSTDOUTb.pl with backticks
stdout from bugSTDOUTb.pl=Running bugSTDOUTc.pl with system()
Hello world!
bugSTDOUTb.pl done
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