use strict;
use warnings;

# get the inputs into an array, one "number" or "n:n" range per array element.
# then:

my @covered; # an array to track the "coverage" of the inputs

# for each input array element {
#    if the element does not contain ":"
#       use it as an array index and set $covered[$element] to some value
#    otherwise
#       split on ":", sort the pieces numerically and assign to $begin, $end
#       $covered[$_] = 'some value' for ( $begin .. $end );
# }
# Once that's done, the only thing left to do is:

my $uncovered = '';
for ( 0 .. $#covered ) {
    $uncovered .= "$_, " unless ( defined( $covered[$_] ));
}
$uncovered =~ s/, $/\n/;
print $uncovered;