Yes--well done!

...I am not sure if it's the correct way...

Tim Toady!

If I may, however, offer the following for you to consider:

#!/usr/bin/perl

use strict;
use warnings;

my $sum  = 0;
my @nums = ();
push( @nums, ( 4, 8 ) );
$sum += $_ for @nums;
my $size    = @nums;
my $average = $sum / $size;
print "$average";
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