b.bat:

@echo off
exit 3
[download]

bb.bat:

@echo off
exit /b 3
[download]

p.pl:

sub test;

test 'b.bat';
test 'call b.bat';
test 'b.bat & exit errorlevel';

test 'bb.bat';
test 'call bb.bat';
test 'bb.bat & exit errorlevel';

sub test
{
    local $\ = "\n";
    print "@_";
    system @_;
    print '  exit code is: ', $? >> 8;
}
[download]

output: b.bat exit code is: 3 call b.bat exit code is: 3 b.bat & exit errorlevel exit code is: 3 bb.bat exit code is: 0 call bb.bat exit code is: 3 bb.bat & exit errorlevel exit code is: 3