You might be interested in how this parses with B::Deparse.

First, the test code:

if ($x1) {
    if ($x2) {
        print "here\n";
    }
}

if ( $x1 && $x2 ) {
    print "here\n";
}
[download]

And now the output under 'deparse,-x9' (the greatest degree of deparsing):

C:\Perl\scripts>perl -MO=Deparse,-x9 mytest.pl
$x1 and do {
    $x2 and do {
        print "here\n"
    }
};
$x1 and $x2 and do {
    print "here\n"
};
mytest.pl syntax OK
[download]

Surprised? :)

They are different, but also similar in more ways than you might initially guess. The biggest difference is nesting.