=over

=item $PROGRAM_NAME

=item $0

Contains the name of the file containing the Perl script being
executed.  On some operating systems
assigning to "C<$0>" modifies the argument area that the ps(1)
program sees.  This is more useful as a way of indicating the
current program state than it is for hiding the program you're running.
(Mnemonic: same as B<sh> and B<ksh>.)

=back