RegEx for matching “A-Z, a-z, 0-9, _” and “.”

Question

I need a regex which will allow only A-Z, a-z, 0-9, the _ character, and dot (.) in the input.

I tried:

[A-Za-z0-9_.] 

But, it did not

Answer 1

Maybe, you need to specify more exactly what didn't work and in what environment you are.

As to the claim that the dot is special in a charackter class, this is not true in every programming environment. For example the following perl script

use warnings;
use strict;

my $str = '!!!.###';
$str =~ s/[A-Za-z_.]/X/g;
print "$str\n";

produces

!!!X###