While working on a solution for Does a file really exist?, I came across some bizarre behavior, that's got me tearing my hair out. Basically, the code below is taken directly from perldoc Date::Calc.

#!/usr/bin/perl -w
#find-missing-files.pl
use strict;
use Date::Calc qw( Delta_Days Add_Delta_Days );

my (@start, @stop);
my $from = $ARGV[0];
my $to = $ARGV[1]; 

$from =~ s/-/,/g; 
$to =~ s/-/,/g;

#@start = $from; print "@start\n";
#@stop = $to;  print "@stop\n";

@start = (1999,05,27);
@stop  = (1999,06,01);

my $j = Delta_Days(@start,@stop);

for ( my  $i = 0; $i <= $j; $i++ ) {
    my @date = Add_Delta_Days(@start,$i);
    printf("%4d-%02d-%02d\n", @date);
}
[download]

As is,

./find-missing-files.pl
[download]

will produce the following output:

1999-05-27
1999-05-28
1999-05-29
1999-05-30
1999-05-31
1999-06-01
[download]

But, uncomment:

#@start = $from; print "@start\n";
#@stop = $to;  print "@stop\n";
[download]

comment this:

@start = (1999,05,27);
@stop  = (1999,06,01);
[download]

and run:

./find-missing-files.pl 1999-05-27 1999-06-01
[download]

it returns:

1999,05,27
1999,06,01
Usage: Date::Calc::Delta_Days(year1, month1, day1, year2, month2, day2
+) at ./test.pl line 19.
[download]

Can anyone explain what's going on here?

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