Question

print hex("0x30"); gives the correct hex to decimal conversion.

What does
print hex(0x30); mean?
The value it’s giving is 72.

Answer 1

hex() takes a string argument, so due to Perl’s weak typing it will read the argument as a string whatever you pass it.

The former is passing 0x30 as a string, which hex() then directly converts to decimal.

The latter is a hex number 0x30, which is 48 in decimal, is passed to hex() which is then interpreted as hex again and converted to decimal number 72. Think of it as doing hex(hex("0x30")).

You should stick with hex("0x30").

$ perl -e 'print 0x30';
48
$ perl -e 'print hex(0x30)';
72
$ perl -e 'print hex(30)';
48
$ perl -e 'print hex("0x30")';
48
$ perl -e 'print hex(hex(30))';
72