One slight correction...

strict 'subs' and strict 'vars' run their checks at compile time, but the third goblin in that group strict 'refs' enables runtime checks.

(sorry, I was inspired by the dancing skeleton on your homenode ...... ;-) )

Consider the following code, which will toss a strict error during runtime, depending on the flip of a coin:

#!/usr/bin/perl -wT
use strict;

use vars qw($foo $bar);

$foo = 'x';
$bar = int(rand(2)) ? 'foo' : \$foo;

print $$bar, "\n";

=OUTPUT (when rand==0)
x

=OUTPUT (when rand==1)
Can't use string ("foo") as a SCALAR ref 
while "strict refs" in use at ./strictrefs.pl
line 9.
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-Blake