Finally I understand your issue, and you are quite right. My regex using $ ignores a single trailing new line character. Vis:

use strict;
use warnings;

my @strs = ("abcdefghijklm\n\n", "abcdefghijklm\n");

for (@strs)
    {
    if (/^[a-zA-Z0-9]{6,20}$/) {
        print "Success: >$_<\n";
    } else {
        print "Invalid string: >$_<\n";
    }
}

[download]

Prints:

Invalid string: >abcdefghijklm

<
Success: >abcdefghijklm
<

[download]

If your first reply had said:

Your solution ignores a trailing newline. Try it with this string: $_ = "abcdefghijklm\n";

I'd have understood your concern straight off. If there was anyone else remaining confused I hope the issue is now clear and that they have learned something, as I have.

DWIM is Perl's answer to Gödel

In reply to Re^7: how should i test whether a string contains between 6 and 20 letters and numbers by GrandFather
in thread how should i test whether a string contains between 6 and 20 letters and numbers by keiusui

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