Also note that it is possible to declare a lexical inside the parentheses of the "if with a block" which leads to an interesting variation of the scope theme:

use strict;
use warnings;

my @L = ('1', '0', '');

while (@L) {
    if (my $x = shift @L) {
        print "\$x is true: <$x>\n";
    } elsif (length $x) {
        print "\$x is false: <$x>\n";
    } else {
        print "\$x is still false<$x>\n";
    }
    # print "$x\n";    # yields a strict error when uncommented
}
[download]

Which prints:

$x is true: <1>
$x is false: <0>
$x is still false<>
[download]

You see that the scope of that lexical is all the way down to the closing curly of the last appendant else-block.

Though it seems the declaration of $x is outside of the if-elsif-else-blocks, its scope actually is only the (complete) conditional.
Uncommenting the print statement outside the conditional yields the "strict vars" error again.