You can use the "pram" operator:

$output = qq(
    @{[ '*' x 80 ]}
);
[download]

but it might be easier to assign the start to a variable before creating the output:

my $STARS = '*' x 80;
my $output = qq(
    $STARS
);
[download]

Using print would print the line of stars in the moment of assignment, and insert the return value of print (hopefully 1) into the created string.