my %vars = (
    test => "Perl",
);

my $content  = "";
my @template = ("Blablabla\n", "<% test %>\n", "blablabla\n");

foreach my $row (@template) {
    $row      =~ s/<% ([A-Za-z0-9]+) %>/$vars{$1}/gix;
    $content .= $row;
    print $row;
}