my $result = '';
for(my $i = 0; $i < $n; $i++) {
    $result .= "$i cat\n\man\n";
}

##</code><code>##

my @lines;
for(my $i = 0; $i < $n; $i++) {
    push @lines, "$i cat";
    push @lines, "man";
}
#print Dumper(\@lines);
my $result = join("\n", @lines);