You might consider a recursive function if you'd like to look ahead to when you need to check four, or four hundred, files...

Or a while loop might be just what you want (and without the overhead of a function).

my $command = pop @ARRAY;

while (shift @ARRAY) {
    die ("Error: " . $!) unless -e;
}

# run your command here -- exec $command, I assume
[download]

This does take a performance hit because of the shift, so if speed is paramount you could just as easily use a for{} loop.

Hope that answers the question.