I'd use something like this (untested):

$/ = "";  # Paragraph node.
my %seen;
open my $fh => "...." or die;
while (<$fh>) {
    next unless /(%FW-\d+-\d+)/;
    print "$1\n$_" unless $seen {$1} ++;
}
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This is just a variant on "remove duplicates".

Abigail