Perl 5 version 26.2 documentation
Interprets EXPR as a hex string and returns the corresponding numeric value. If EXPR is omitted, uses $_ .
A hex string consists of hex digits and an optional
xprefix. Each hex digit may be preceded by a single underscore, which will be ignored. Any other character triggers a warning and causes the rest of the string to be ignored (even leading whitespace, unlike oct). Only integers can be represented, and integer overflow triggers a warning.