@ARGV is a special variable in Perl that stores arguments, either from the command line when you first initiate the script. For example:

#!/usr/bin/perl -w
use strict;

my $length = @ARGV;

## If the number of arguments is less than two, it dies
## else it shifts them off of the array and into the
## variables

if($length<2){
  die"Not enough arguements!\n";
}else{
  my $arg1 = shift;
  my $arg2 = shift;
}
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UPDATE: Corrected variable name.
UPDATE 2: And as runrig reminded me, there is also a $ARGV variable which contains the filename of an open file when you call it like this: <>

TStanley
--------
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about this script for Hamlet they've worked out
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