Assuming you want days between date 1 and date 2 and between date 2 and date 3 etc. then it's a simple enough loop:

#!/usr/bin/env perl 
use strict;
use warnings;
use Date::Calc 'Delta_Days';

my @dates = ('2005-09-27', '2019-12-22', '2018-10-24', '1999-12-31');
my @start = split (/-/, shift @dates);
while (0 < @dates) {
    local $" = '-';
    my @end = split (/-/, shift @dates);
    print "@start to @end is " . Delta_Days (@start, @end) . " days\n"
+;
    @start = @end;
}
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