#!/usr/bin/perl

use warnings;
use strict;
use diagnostics;

my $foo = 1;

if($foo = 2) {
        print "Boo!\n";
}

##</code><code>##

Found = in conditional, should be == at hole.pl line 8. (#1)
    (W syntax) You said
    
        if ($foo = 123)
    
    when you meant
    
        if ($foo == 123)
    
    (or something like that).

Boo!