#!/usr/bin/perl -w

# Array containing all lines
my @screen = ( ' 'x70 . "\n" ) x 20;

# Array of possible (equiprobable) characters
my @char = split //, '                     *|';

while(1) {
    print join '', @screen;
    # Drop last line
    pop @screen;
    # Put a new line on top
    unshift @screen, join ( '', map { $char[ rand(@char) ] } (1..70) ) . "\n";
    # Sleep for 0.1 seconds
    select(undef, undef, undef, 0.1);
}