What you wrote is easy to read but, for me, the following is easier...

my @rec;
while (<$fh>) {
    my $entry = parse_line($_);
    if (@rec and $entry->{key} ne $rec[0]->{key}) {
        process_rec(\@rec);
        @rec = ();
    }
    push @rec, $entry;
}
process_rec(\@rec);

sub parse_line {
    my ($line) = @_;
    chomp($line);
    my %entry;
    # ...
    return \%entry;
}

sub process_rec {
    my ($rec) = @_;
    return if ! @$rec;
    # ...
}
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