#sub foo() which sets $var can never fail for such and such reason
defined($var) or die "\$var must not be undef.\n" 

#I'm too lazy to make it work properly for all lists
(@list > $XXX) or warn "This algorithm is only ideal for lists no".
                       " bigger than $XXX elements." 

#cross platform compatibility is comming in version 9.0
($^O eq 'MSWin32') or die "Platform not supported"