print "Site $_ is $sites[$_-1]\n" for 1 .. 3;
would be better written as
print "Site $_ is $sites[$_-1]\n" for 1 .. @sites;
or
print "Site ", $_+1, " is $sites[$_]\n" for 0 .. $#sites;

Noone said the index needed to be printed:
print "$_\n" foreach @sites;