se strict; use warnings;
use Test::More;
use List::Util 'pairfirst';

my @data = (
    { id =>   1, start => 2, end => 3 },
    { id =>   2, start => 3, end => 4 },
    { id =>   3, start => 4, end => 5 }, # fail
    { id =>  42, start => 6, end => 7 },
    { id => 666, start => 7, end => 8 },
    { id => 999, start => 8, end => 9 },
);

my @failed = pairfirst { $a->{'end'} ne $b->{'start'} } @data;
is( @failed, undef, 'sequencing' )
  or diag sprintf 'ID %s and ID %s are not sequential', map { $_->{'id'} } @failed;

done_testing;
__END__