use strict;
use warnings;
use feature qw (say signatures);
no warnings qw(experimental::signatures);

use IO::Prompter [
    -style => 'bold blue',
    -echostyle => 'bold magenta',
];
use Term::ANSIColor 5.0;

my @nums_under_255 = qw{0 26 51 77 102 127 153 179 204 230 243};

say '';

for my $r (@nums_under_255, 255) {
    for my $g (@nums_under_255, 255) {
        print '  ';

        for my $b (@nums_under_255) {
            print colored(text("r${r}g${g}b${b}"), join(' on_', fg($r,
+ $g, $b), "r${r}g${g}b${b}"));
        }

        say colored(text("r${r}g${g}b255"), join(' on_', fg($r, $g, 25
+5), "r${r}g${g}b255"));
    }
}

say '';

my $rgb;

while (1) {
    $rgb = prompt 'Convert hex to decimal rgb (or just hit "Enter" to 
+quit): ', -return => '';
    # Fix for MSWin -- see https://rt.cpan.org/Public/Bug/Display.html
+?id=118255
    $rgb =~ s/\R\z//;
    unless (length $rgb) {
        say '';
        last;
    }

    if ($rgb =~ /^([0-9a-fA-F]{2})([0-9a-fA-F]{2})([0-9a-fA-F]{2})$/) 
+{
        my $ansi_rgb = sprintf 'r%dg%db%d', map hex, $1, $2, $3;
        print colored(' --> [', 'bold white');
        print colored(' ' x 8, "$ansi_rgb on_$ansi_rgb");
        print colored('] --> ', 'bold white');
        say colored($ansi_rgb, 'bold cyan');
    }
    else {
        say colored("\nERROR: '", 'r255g0b0 on_r51g51b51'),
            colored($rgb, 'r255g255b0 on_r51g51b51'),
            colored(
                "' is invalid. Six hexadecimal characters are expected
+; such as in the table above.",
                'r255g0b0 on_r51g51b51'
            );
    }
}

sub fg ($r, $g, $b) {
    #return $r + 2 * $g + $b > 204 ? 'black' : 'white';
    return "r${r}g${g}b${b}";
}

sub text ($str) {
    return sprintf ' %02x%02x%02x ', $str =~ /^r(\d+)g(\d+)b(\d+)$/;
}
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