C:\>perl -e "print 'different' if 1.23456789012345e15 != 1.234567890123454e15;"
different
C:\>perl -e "print 'different' if 1.23456789012345e15 != 1.2345678901234544e15;"
different
C:\>perl -e "print 'different' if 1.234567890123454e15 != 1.2345678901234544e15;"
different