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

package Random_Char;
sub TIESCALAR { bless {}, $_[0] }
sub STORE { return 1 }
sub FETCH {open(I,$0);my $l;while(<I>){$l=$_ and last if$.==(caller)[2]}
    $l =~ s/^.*=\s*(["'])(.*)\1\s*=~.*$/$2/;my @c=keys%{{
    map{$_=>undef}split//,$l}};return $c[rand @c];
}

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