Check characters inside string for their Unicode value - perl

Question

I would like to replace characters with certain Unicode values in a variable with dash. I have two ideas which might work, but I do not know how to check for the value of character:
1/ processing variable as string, checking every characters value and placing these characters in a new variable (replacing those characters which are invalid)
2/ use these magic :-)
$variable = s/[$char_range]/-/g;
char_range should be similar to [0-9] or [A-Z], but it should be values for utf-8 characters. I need range from 0x00 to 0x7F to be exact.

Answer 1

The following expression should replace anything that is not ASCII with a hyphen, which is (I think) what you want to do:
s/[\N{U+0080}-\N{U+FFFF}]/-/g

Answer 2

There's no such thing as UTF-8 characters. There are only characters that you encode into UTF-8. Even then, you don't want to make ranges outside of the magical ones that Perl knows about. You're likely to get more than you expect.
To get the ordinal value for a character, use ord:
use utf8;
my $code_number = ord '😸'; # U+1F638
say sprintf "%#x", $code_number;
However, I don't think that's what you need. It sounds like you want to replace characters in the ASCII range with a -. You can specify ranges of code numbers:
s/[\000-\177]/-/g; # in octal
s/[\x00-\x7f]/-/g; # in hexadecimal
You can specify wide character ordinal values in braces:
s/[\x80-\x{10ffff}]/-/g; # wide characters, replace non-ASCII in this case
When the characters have a common property, you can use that:
s/\p{ASCII}/-/g;
However, if you are replacing things character for character, you might want a transliteration:
$string =~ tr/\000-\177/-/;