use Locale::Hebrew::Calendar;
my ($dd,$mm,$yy) = ("04","05","-1806");
# Gregorian to Jewish
my ($d, $m, $y) = Locale::Hebrew::Calendar::g2j($dd, $mm, $yy);
print "G2J: $d/$m/$y\n";

$perl hebrewcal.pl 
G2J: 11/7/1954