Here's my lazy attempt
use strict;
## I've lazily pre-sorted these ;)
my @ars = (
[ qw/ 1 2 3 4 5 / ],
[ qw/ 1 2 3 4 6 / ],
[ qw/ 2 3 4 6 7 / ],
);
for(@ars) {
print "broken list: @$_\n" and next
if $_->[0] != 1;
my($i, $n) = 0;
$n = $_->[$i]
while $i <= $#{$_} and $_->[$i] + 1 == $_->[++$i];
print "woo: @$_\n"
if $n == $_->[-1];
print "doh: sequence broke at index ${\($i - 1)} (@$_[$i - 1,$i])\n"
if $n != $_->[-1];
}
__output__
woo: 1 2 3 4 5
doh: sequence broke at index 3 (4 6)
broken list: 2 3 4 6 7
So basically it checks the sequence by iterating through the pre-sorted array until there's a gap in the sequence. Then just checks whether the end value is the same as last value seen in the iteration.
HTH
_________
broquaint