An ingenious way to find Java on POSIX systems

This is Perl code. _java_bin returns the full path to the java executable.

From http://search.cpan.org/~dolmen/DateTime-TimeZone-HPUX-1.04/lib/DateTime/TimeZone/HPUX.pm

our @JAVA_HOMES = (
    '/opt/java1.4',
);

{
    my $_java_bin;
    sub _java_bin
    {
        return $_java_bin if defined $_java_bin;
        $_java_bin = ''; # Default value: java not found (false)
        foreach (
                (map { ("$_/jre/bin/java", "$_/bin/java") }
                     (exists $ENV{JAVA_HOME} ? ($ENV{JAVA_HOME}) : ()),
                     @JAVA_HOMES,
                ),
                (map { "$_/java" } split(/:/, $ENV{PATH}) ),
            ) {
            next unless -x "$_";
            $_java_bin = $_;
            last;
        }
        return $_java_bin;
    }
}