why need my in a foreach loop?

[szabgab]

use strict;
use 5.010;

foreach my $word (qw(abc def ghi)) {
   say $word;
}

When using strict perl requires to declare even the loop variable of a foreach loop. Why is that? After all the $word variable in the above example is an alias to the values and won't have any effect outside of the loop. Even if written this way:

use strict;
use 5.010;

my $word = "hello";
foreach $word (qw(abc def ghi)) {
   say $word;
}
say $word;  # word is "hello" here

Why is this code not allowed?

use strict;
use 5.010;

foreach $word (qw(abc def ghi)) {
   say $word;
}
# generate syntax error if $word is used here