why not make your code a little bit more readable (and a bit more perl-ish), by changing this:

# assign valid strings
my @valid = (
  '$1',
  '$1.11',
  '$.11',
  '-$1',
  '-$1.11',
  '-$.11',
  '$-1',
  '$-1.11',
  '$-.11',
);
[download]

to something like this, using the qw() operator:

# assign valid strings
my @valid = qw(
   $1
   $1.11
   $.11
  -$1
  -$1.11
  -$.11
   $-1
   $-1.11
   $-.11
);
[download]

Of course, if you ever have any spaces in your future tests, this goes mostly out the window, but since your strings seem to fit just fine, I would say it will be a little easier to read and maintain. So long as no one reads the $- and $1 as variables, you should be good to go.