The attached code will join two email lists with a comma between them but if either is empty then no comma is added and if both are empty then '' is returned.

Is there a better or more Perlish way to do this? I just confirmed MIME::Lite doesn't care if there is an extra comma in front or back but I have a subroutine that returns if the address field is empty without attempting to send. 

#!/usr/bin/perl
use strict;
use warnings;

my $list1 = 'jj@xyz.com,kk@xyz.com';
my $list2 = 'aa@xyz.com';

print join_email_lists( $list1,$list2),"\n"; #want comma separated
print join_email_lists( ''    ,$list2),"\n"; #no comma in front
print join_email_lists( $list1,''    ),"\n"; #no comma behind
print join_email_lists( ''    ,''    ),"\n"; #want ''

sub join_email_lists {
    my ($a1,$a2) = @_;
    return $a1 . ',', $a2 if $a1 and $a2;
    return $a1 if $a1;
    return $a2 if $a2;    
    return '';
}

[download]

Update: The email lists come from a config file in my production code and I wanted to make sure it still works if someone clears one or both email list. I tried to simplify things but leaving the long names $error_only_list and $email_always_list would have made things clearer.

When I put this code into production it would only return the first list. Then I noticed I had a comma where it should have been a '.' in the first return statement.

In reply to join email lists with comma unless one list is empty by Gulliver

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