CODEWITHSUNDEEP
perl
MarsEclipse
MarsEclipse

Reputation: 55

run a subroutine by using argument

My code:

my $aaa = "abc";   
sub myp{
  print "$_";
}
myp($aaa);

I hope myp can print the argument it get. But it said Use of uninitialized value $_ in string at ./arg line 17.

Upvotes: 0

Views: 82

Answers (2)

sergiotarxz
sergiotarxz

Reputation: 540

I usually do something like:

my $first_arg = shift @_;
my $second_arg = shift @_;

You can also use the method of the other response:

my ($first_arg, $second_arg) = @_;

But be careful saying:

my $first_arg = @_;

Since you will get the number of arguments passed to the subroutine.

When you refer to $_ you are referencing the default string variable, you probably want in this case to refer @_, if you want to get a specific argument, you must say $_[narg], be also careful passing arrays to subroutines if you do:

some_sub(@myarray);

You will pass the entire array as it was the argument list, instead you should say:

some_sub(\@myarray);

Upvotes: 1

user149341
user149341

Reputation:

The arguments to a subroutine in Perl are passed in the @_ array. This is not the same as the $_ variable.

A common idiom is to "unpack" these arguments in the first line of a function, e.g.

sub example {
   my ($arg1, $arg2) = @_;
   print "$arg1 and $arg2";
}

It's also possible to refer to arguments directly as elements of @_, e.g. as $_[0], but this is much harder to read and as such is best avoided.

Upvotes: 5

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