Rule 1: thou shallt not read the lines yourself! When you read with the diamond operator, (embedded) line separation gets lost. So instead of:

my $csv = Text::CSV_XS->new ({
    quote_char => '"',
    sep_char   => ":",
    binary     => 1,
    });
my @columns;
open (FILE, $csvfile) or die "Can't open $csvfile: $!";
while (<FILE>) {
    $csv->parse ($_) or die "parse() failed: " . $csv->error_input ();
    my @data = $csv->fields ();
    for my $i (0..$#data) {
        push @{$columns[$i]}, $data[$i];
        }
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Use:

my $csv = Text::CSV_XS->new ({
    binary             => 1,
    auto_diag          => 1,
    allow_loose_quotes => 1,
    });
my @columns;
open my $fh, "<", $file or die "$file: $!";
while (my $row = $csv->getline ($fh)) {
    for (@$row) {
        my ($key, $value) = split m/"?:"?/, $_, 2;
        # ... 
        }
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