[PerlChina] Question about if (@array)

Hi, all

Would you explain the output of the following perl codes?

question 1:
Is the sentence "if (@array) " same as "if ( scalar(@array) )"??
question 2:
what's the difference of "undef $variable " and "delete $variable"??

Thanks,
Ray

-------------------------------------------
code----------------------------------
#!/usr/bin/perl

use strict;
use warnings;

my @host = ();
my @host1 = ('fdfd', 'fdfdfd');
my @host2 = undef;

if ( @host ) {
print "host ok\n";
} else {
print "host fail\n";
}

if ( @host1 ) {
print "host1 ok\n";
} else {
print "host1 fail\n";
}

if ( @host2 ) {
print "host2 ok\n";
} else {
print "host2 fail\n";
}
-------------------------------------------
code----------------------------------

and the output is :
host fail
host1 ok
host2 ok

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