Well, you could do this if you don't mind tinkering with special variables:

{  # localizing $" is a good idea...
  local $"="";
  if ($string =~ m#^[@$chars]$#) {
     print "OKie! $string is a subset of @$chars\n";
  } else {
     print "Bad $string! Bad!\n";
  }
}
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$" sets the string that perl puts between items in an array when the array is interpolated in a doublequoted string. BTW, regexen are treated like doublequoted strings. You can stick variables in there, backwhack for special characters like \n and much more. =)

--
$you = new YOU;
honk() if $you->love(perl)