Question

This Perl code is part of the variable declaration at the beginning of a piece of code. What does it mean?

my $EXPLICIT_YEAR = $ALL_PAGES ? 0 : ($store{year} || $current_year);

Answer 1

It’s equivalent to this:

my $EXPLICIT_YEAR;
if ($ALL_PAGES) {
    $EXPLICIT_YEAR = 0;
}
else {
    # $EXPLICIT_YEAR = $store{year} || $current_year;
    if ($store{year}) {
        $EXPLICIT_YEAR = $store{year};
    }
    else {
        $EXPLICIT_YEAR = $current_year;
    }
}

The $conditional ? $true : $false portion is a ternary if.
The $store{year} || $current_year portion uses the fact that the || operator returns the first value that evaluates to true, allowing $current_year to be used if $store{year} is “false” (zero, empty string, etc.)