my @arr = ( 1, 2, 3, 0x47 ); are numeric literals, see Scalar value constructors. In the source code they can look like 12345 or 4_294_967_296 or 0xff or 0377 or 0b011011 and will all be converted to numbers and stored as numbers. my @arr = qw/ 1 2 3 0x47 /; are strings, see qw//, it's the same as writing my @arr = ( "1", "2", "3", "0x47" );. In the source code, 0x47 is different from "0x47", the first one means 71 and the second one is a string with four characters. Strings will only be automatically converted to numbers if they are plain integers. If you want to know if a string will automatically convert to a number, you can use looks_like_number from Scalar::Util. "0x47" is not a plain integer, it's got an x character. Use oct to convert that string to a number, oct it does octal, 0x123 and 0b101 formats, or use hex which only does hexadecimal.