#!/usr/bin/perl
use strict;
use warnings;

package Random_Char;
use PadWalker 'peek_my';
sub TIESCALAR { bless {}, $_[0] }
sub STORE { return 1 }
sub FETCH {my @c=keys%{{map{$_=>undef}split//,${peek_my(1)->{'$string'}}}};return $c[rand @c];}

package main;
tie my $rand_char, "Random_Char";
my $string = 'One bright day in the middle of the night';
my ($char) = $string =~ /($rand_char)/;
print "$char\n";