Here is how to use a character class to achieve that.

use strict;
use warnings;

use Test::More;

my @good = (
    'a',
    '9',
    '_',
);

my @bad = (
    '-',
    '$',
    '?',
);

my $re = qr/[\w.]/;

plan tests => @good + @bad;

like   $_, $re, "match for '$_'"    for @good;
unlike $_, $re, "no match for '$_'" for @bad;
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