use strict; #always and forever, amen.
use warnings;  #or else.

my $argument=$ARGV[0]; 
#@ARGV is an array containing the arguments supplied. We're taking the first value.
print "\n$argument"; 
#This here will show you exactly what has been put into $argument.
##</code><code>##


$bar='Hello,';
$baz=' world!';
foo($bar, $baz); 
#calls the foo subroutine with $bar and $baz as arguments

sub foo {
  print for @_;
#will first print out the contents of $bar, then $baz because 
#those are the arguments given.
}

##</code><code>##

foo("square", 3);

sub foo{
  my ($shape, $size) = @_;
}