The directive is #line 15, any message produce on the line after this will be reported as line 15, line 16 for the next and so on. If you have AS, it would be much easier to us the pl2bat.bat command that comes with the distribution. Look in x:\perl\bin or where ever you have your perl installed.

It builds a bat from the .pl and adds the appropriate #line nn bit for you.

If you have AS 5.6.1, modify the url behind this [file://localhost/X:/perl/html/faq/Windows/ActivePerl-Winfaq4.html] to reflect your installation and it will take you to the documentation of pl2bat and other good stuff