if we're golfing this, you can reduce that line a bit:

sub sqroot {
#23456789_123456789_123456789_123456
$g++;$g=($_[0]/$g+$g)/2for-1..pop;$g
}
[download]

jynx

update: d'oh, i was erroneously fooled by my browser when entering the snippet, it's actually 36 characters...