This seems to be such an elegant little script for dealing with character classes but also the hyphen. I replicated it and save such scripts for the rainy day when I wonder how to do exactly this. I changed the data slightly to satisfy myself that that hyphen matched.

$ ./1.hippo_regex.pl 
1..7
ok 1 - a matched
ok 2 - - matched
ok 3 - (321) matched
ok 4 - a(321-)_HGF matched
ok 5 - "@$ not matched
ok 6 - ~ not matched
ok 7 - [{ not matched
[download]

Source:

#!/usr/bin/perl -w
use 5.011;
use Test::More;

my @good = (
    'a',
    '-',
    '(321)',
    'a(321-)_HGF'
);

my @bad = (
    '"@$',
    '~',
    '[{'
);

my $re = qr/^[a-zA-Z0-9_()-]+$/;

plan tests => @good + @bad;

for my $str (@good) {
    like ($str, $re, "$str matched");
}
for my $str (@bad) {
    unlike ($str, $re, "$str not matched");
}
[download]