Assert

assert

die

1 Python

assert 1 == 1
assert 1 == 2
# AssertionError

assert 1 == 2, 'Oh, my goodness.'
# AssertionError: Oh, my goodness.

2 Perl

die unless 1 eq 1;
die unless 1 eq 2;
# Died at - line 2

die("Oh, my goodness.") unless 1 eq 2;
# Oh, my goodness. at - line 1.

use Carp::Assert;
assert(1 eq 2);