#!/usr/bin/perl
use warnings;
use strict;
my @data = ( [1 .. 3], [4 .. 6], [7 .. 9] );

norm(\@data);

print join(", ", @{$_}), "\n" for @data;

sub norm{
    my $ar = shift;
    for(@$ar){ # iterates down @data
        my $norm=(($$_[0])**2+($$_[1])**2)**(1/2); #calculates the norm
        $$_[3] = $norm;
    }
}