for my $i (0 .. $#titles){
    ...
}

##</code><code>##

perl -wMstrict -E 'my @x=(qw(a b c)); say "$_: $x[$_]" for (0..@x)'
0: a
1: b
2: c
Use of uninitialized value in concatenation (.) or string at -e line 1.
3: 

##</code><code>##

perl -wMstrict -E 'my @x=(qw(a b c)); say "$_: $x[$_]" for (0..$#x)'
0: a
1: b
2: c