Perl Debugged

10.1. A Bit Illogical

Perl has several ways of saying and and or:

Table 10-1. And, Or, and Xor Operators in Perl

Operation	AND	OR	XOR
bitwise (non-short-circuiting)	&	|	^
logical (high precedence)	&&	||
logical (low precedence)	and	or	xor

(There is no high-precedence logical XOR operator.) The consequences of picking an operator from the wrong row are usually annoying mistakes like

open (FH, $file) | die "Error opening $file: $!\n";

which dies whether or not the open succeeds, because the | operator is strictly a bitwise arithmetic or string operator, which evaluates both of its operands so that it can return the result of ORing their bits together. In this case, you want ||, which is a logical operator that evaluates its left-hand side and ...