$var=chr(0x0a).chr(0x0a).chr(0x0a).chr(0x01);
# OR
$var=v10.10.10.1;  #using the v-string notation if your perl is new enough
# OR
$var=pack "CCCC", 10, 10, 10, 1;
# OR (probably best yet)
$var=inet_aton 0x0a0a0a01;