The following (flawed, see below) experiment (prints out the memory location of the static hash) seems to suggest that Perl indeed creates the hash only once:

#!/usr/bin/perl
sub static_hash {

    print { one => 1, two => 2 };
    print $/;
}

static_hash;
static_hash;
static_hash;
[download]

planz$ perl /tmp/static.pl 
HASH(0x1801380)
HASH(0x1801380)
HASH(0x1801380)
[download]

Update: Okay, forget about that, this just shows that a hash gets created in the same memory location. It could still be a new hash every time. In fact, changing the experiment to use a fresh hash yields exactly the same output:

#!/usr/bin/perl
sub static_hash {

    print { one => $_[0], two => time };
    print $/;
}

static_hash(8);
static_hash(9);
static_hash(10);
[download]