The exit keyword

exit finishes the execution of the program after valuating EXPRESSION. It returns with this value.

Although exists can be called on arrays also, its behaviour strongly depends to the use of delete on arrays, having a much less clear behaviour.

  exit EXPRESSION
  exit

print "Exists\n"    if exists $hash{$key};
print "Defined\n"   if defined $hash{$key};
print "True\n"      if $hash{$key};