what is benefit of unless ?

[Anonymous Monk]

I think unless statements are similar to if statements.But if-else stmt gives us more flexibility then unless.So is there any specific use of this . please reply soon. regards, barun parichha

[holli]

$ cat input
foo



bar
$ perl -ne 'print unless /^$/../^$/' input
foo
bar
$ perl -ne 'print if not /^$/../^$/' input
foo
bar
$ perl -ne 'print if ! /^$/../^$/' input
foo

bar

The unless statement is equivalent to if not, but is different from if ! due to the associativity and precedence rules covered in perlop. A benefit of this behavior allows the reduction of runs of blank lines to a single blank line.

taken from here

[Anonymous Monk]

You can use "else" with "unless".

"unless" means "if not", so it reverses the meaning of an "if" comparison.

See perlsyn for details.

Please read Where should I post X? and How (Not) To Ask A Question.

[Anonymous Monk]

is this the equivalent code for " unless(condition)" ? if !(condition) { ... ... } else { ... ... } reply soon, barun parichha

[merlyn]

unless ($boolean) { ... }

is nearly completely equivalent to:

if (not $boolean) { ... }

(The slight difference is in the "last expression evaluated" return value for a subroutine, but that's only a minor distracting point.)

[prasadbabu]

It is not similar statement.

$a = 10;
print "if stmt true" if ($a == 10);
print "unless" unless ($a == 10);