Useless use of string in void context at

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

hi,

use strict;                                                           
+          
use warnings;                                                         
+          
use autodie;                                                          
+          

my @test_svc = (
    "test\@customer1.service", "test\@customer2.service",
    "test\@custome3.service",  "test\@customer4.service",
    "test\@customer5.service", "test\@customer6.service",
);

my @customers = qw/ customer1 customer2 customer33 customer4 customer5
+ /;

for my $cust (@customers) {
    if ( my ( $matched ) = grep $_ =~ $cust, @test_svc ) {
        print "$cust matches:\t $matched\n";
    }
    else {
        "no matches for $cust\n";
    }
}
[download]

When I run it:

$ perl /tmp/kk.pl 
Useless use of string in void context at /tmp/kk.pl line 38.
customer1 matches:     test@customer1.service
customer2 matches:     test@customer2.service
customer4 matches:     test@customer4.service
customer5 matches:     test@customer5.service
[download]

So it correctly sees the matches, but I miss the mismatch. What is wrong with my crappy script? ;-)

TIA.

Comment on Useless use of string in void context at Select or Download Code

Replies are listed 'Best First'.
Re: Useless use of string in void context at by tybalt89 (Monsignor) on Oct 05, 2017 at 20:05 UTC
Strings don't print themselves: `print "no matches for $cust\n";` [download]	[reply] [d/l]
Re^2: Useless use of string in void context at by natxo (Scribe) on Oct 05, 2017 at 20:17 UTC
doh! Thanks ;-), time for bed now.	[reply]
Re: Useless use of string in void context at by LanX (Saint) on Oct 05, 2017 at 20:07 UTC
> What is wrong with my crappy script? ;-) You don't print and Perl is warning you that it's a `Useless use of string in void context` giving you even the line number. `"no matches for $cust\n"; # <--- Wot ?` edit FWIW I would have collected all results in an array (and other changes improving readability) `use strict; use warnings; use autodie; my @test_svc = ( "test\@customer1.service", "test\@customer2.service", "test\@custome3.service", "test\@customer4.service", "test\@customer5.service", "test\@customer6.service", ); my @customers = qw/ customer1 customer2 customer33 customer4 customer5 + /; for my $cust (@customers) { if ( my @matches = grep { /$cust/ } @test_svc ) { print "$cust matches:\t", (join "\t", @matches) ,"\n"; } else { print "no matches for $cust\n"; } }` [download] Cheers Rolf _{(addicted to the Perl Programming Language and ☆☆☆☆ :) Je suis Charlie!}	[reply] [d/l] [select]
Re: Useless use of string in void context at by GrandFather (Saint) on Oct 05, 2017 at 20:25 UTC
Perhaps the missing print in the else clause? You provide the string, but not print in front of it. Premature optimization is the root of all job security	[reply]

edit