Fletch's solution needs a slight bit of tweaking. It matches a false positive with "every" being in the word "very", since the "e" matches twice. 
# are all letters of X in Y?
sub inclusive {
  my ($src, $dst) = @_;
  my %p;
  # I don't know which of these is optimal...
  # so I leave it up to you
  # for my $c (split //, $src) {
  while (defined(my $c = chop $src)) {
    return if !($p{$c} = 1 + index($dst, $c, $p{$c} || 0))
  }
  return 1;
}

[download]
That's a better approach, in my opinion. You can use a regex too, but that would be a terribly ugly approach.

_____________________________________________________
Jeff[japhy]Pinyan: Perl, regex, and perl hacker.
s++=END;++y(;-P)}y js++=;shajsj<++y(p-q)}?print:??;

In reply to Re: Does a regex exist for this problem? by japhy
in thread Regex to find intersection of two words by 2501

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.