See __PACKAGE__ in perldata.

    #!/usr/bin/perl -wl

    print __PACKAGE__;

    package My::Package;

    print __PACKAGE__;

    __END__

    Prints:
    main
    My::Package
[download]

Update: As per the comment below, if you want the filename and not the package name then you should use __FILE__, also in perldata.

--
John.