Extracting info for DHCP option

With version 11.5.4 and 12 produces warnings about curly braces:

There were warnings: /Common/rule_dhcp_mac_sticky_example:16: warning: [use curly braces to avoid double substitution][$i] /Common/rule_dhcp_mac_sticky_example:22: warning: [use curly braces to avoid double substitution][$i] /Common/rule_dhcp_mac_sticky_example:23: warning: [use curly braces to avoid double substitution][0x$length_hex] /Common/rule_dhcp_mac_sticky_example:31: warning: [use curly braces to avoid double substitution][$i] /Common/rule_dhcp_mac_sticky_example:32: warning: [use curly braces to avoid double substitution][0x$length_hex] /Common/rule_dhcp_mac_sticky_example:38: warning: [use curly braces to avoid double substitution][$i]