OK, I bow humble before thee, honorablest Perl monks:

What is this 'EOUsage' in the code below? And what is that funky '$0' variable? I obviously didn't find it too helpful, but here's what the perldoc says about $0:

Contains the name of the file containing the Perl script being executed. On some operating systems assigning to ``$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 sh and ksh.)

I'm guessing, from the way it looks, it automatically comments out the lines but how exactly does it work? Here's the subroutine code I have questions on, edited for brevity: 

sub usage
{
    $0 =~ s#.*/##;
    print STDERR <<EOUsage;

Usage: $0 [options]

where options are:
     [-v         ] | [--version                       ]

[more of the same...deleted...deleted...deleted...deleted]

     [-db <n>    ] | [--debug <n>                     ]
     [-pm/+pm    ] | [--preformat-marker / --nopreformat-marker ]

  More complete explanations of these options can be found in 
  comments near the beginning of the script.

EOUsage
#     [-T <t>:<r> ] | [--tag <tagname>:<regexp>        ]
}

[download]

Any other insights into what this subroutine is doing is much appreciated. Thanks!

2001-03-29 Edit by Corion : Changed title

In reply to Here document syntax, what is $0 (was: Newbie need a clue) by nysus

Title:
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