Return Value in Subroutine

rose has asked for the wisdom of the Perl Monks concerning the following question:

Hi Monks,

I have few confusion is as follows. It would be very helpfull if you clear.

I have perl file name a.pl

#!/usr/local/bin/perl

use b;
MAIN: {
my $value;
b::test($value);
print "\nVALUE = $value\n";
}
[download]

b.pm has following code.

package b;
print "\nINSIDE-PACKAGE\n";

sub test {
my ($value) = @_;
$value="This is value return from sub\n";
return $value;   ## If I comment this
}
1;
[download]

This code is working well and the return $value also printing.

My doubt is, if I comment return $value;, the return will not print. Is there any option to print if I don't use return

Please sugget me..

Thanks!!!
Rose

Comment on Return Value in Subroutine Select or Download Code

Replies are listed 'Best First'.
Re: Return Value in Subroutine by ikegami (Patriarch) on Jul 16, 2007 at 16:44 UTC
`test`'s `$value` and `MAIN`'s `$value` are completly different variables despite the similarity in their names. Assigning to one will not change the other. Fortunately, since parameters are passed by reference in Perl, you can change a variable in the caller by modifying the parameter (`$_[0]`) as opposed to a copy of it (`$value`). `sub test { $_[0] = "new value"; } { my $var = "old value"; print("$var\n"); test($var); print("$var\n"); }` [download] If you wanted to use a meaningful name instead of `$_[0]`, you could create an alias using Data::Alias or as follows: `sub test { # alias my $arg = $_[0]; our $arg; local arg = \$_[0]; $arg = "new value"; } { my $var = "old value"; print("$var\n"); test($var); print("$var\n"); }` [download] Update*: Added aliasing bit.	[reply] [d/l] [select]
Re^2: Return Value in Subroutine by citromatik (Curate) on Jul 16, 2007 at 16:59 UTC
Or maybe pass a reference in the first place (making more obvious that you expect $var to be changed): `sub test { my ($val) = @_; $$val = "new_value"; } { my $var = "old value"; print("$var\n"); test(\$var); print("$var\n"); }` [download]	[reply] [d/l]
Re: Return Value in Subroutine by Ploux (Acolyte) on Jul 16, 2007 at 17:41 UTC
I don't see how your current code is working. Change this: `b::test($value);` [download] to this: `$value = b::test();` [download] With or without the return statement, the the last variable to be set (which is $value) will be returned.	[reply] [d/l] [select]