Hmm, what are you expecting and how are you calling your function?

It seems to "work" for me. 

#!/usr/local/bin/perl -w
use strict;

sub find_holes {
  my @list = @{ shift() };
  @list = sort { $a <=> $b } @list;
  my $low = $list[0];
  my $high = $list[-1];
  my %isthere = map { $_ => 0 } ($low..$high);
  $isthere{$_} = "yes" for @list;
  my @vacancies = grep { not $isthere{$_} } sort keys %isthere;
  return \@vacancies;
}

my @foo = qw(1 2 5 6 9);
my $vac = find_holes(\@foo);
print "@$vac\n";
__END__

$ ./holes.pl 
3 4 7 8

[download]

In reply to Re: Finding missing elements in a sequence (code) by kwoff
in thread Finding missing elements in a sequence (code) by deprecated

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.