Include a perl variable inside a bash command in a perl script - bash

Question

For example:
#!/usr/bin/perl
...
my $host = $db_conf->{host};
my #cmd = ('date',$host);
system(#cmd);
So the results i am expecting is:
Fri Aug 11 15:41:28 CST 2017 db-test-1
With db-test-1 being the hostname.
Here is my entire code:
#!/usr/bin/perl
use strict;
use warnings;
use 5.010;
use DBI;
use Encode;
use IO::File;
use JSON;
use utf8;
BEGIN {
binmode STDERR, ':utf8';
binmode STDIN, ':utf8';
binmode STDOUT, ':utf8';
}
INIT {
my #databases = </kkcorp/kksecret/db-*/db.json>;
foreach my $filename (#databases) {
my $fh = IO::File->new($filename, 'r') or croak $!;
my #buf = <$fh>;
my $str = join '', #buf;
$fh->close;
my $db_conf = decode_json $str;
my $entry = int(rand(scalar(#{$db_conf})));
$db_conf = $db_conf->[$entry]->{writer}->{params};
my $host = $db_conf->{host};
my $dbname = $db_conf->{dbname};
my $password = $db_conf->{password};
my $username = $db_conf->{username};
my $wsrep_check = `mysql -h $host -u $username -p$password < /authdir/auto_inc_script.sql`;
$hosti
if (index($wsrep_check, 'Value: Synced') != -1) {
my #cmd = ('date ${host}');
system(#cmd);
my #wsrep_check_lines = split /\n/, $wsrep_check;
my #table_name = grep { /Synced/ } #wsrep_check_lines;
for my $line (#table_name){
say STDERR $line;
}
say '';
}
}
}
__END__
So what i am trying to achieve in in the two statements right after the beginning of the "if" statement. The code runs fine, but ignored the ${host} variable without displaying any output for it.
Below is my results:
Fri Aug 11 17:13:19 CST 2017
ok Value: Synced
Fri Aug 11 17:13:20 CST 2017
ok Value: Synced

Answer 1

system is very powerful but also very dangerous. It is easy to make disasters, consider, if you feed it with an rm, better if you make absolutely clear what parameters rm gets before running system.
For this reason I always follow this practice:
create the commad string
print the command string
check if print representation is what i want to send to the shell
add the system part
Here is an example, from the command line:
perl -e ' $var = "Hello"; $cmd = qq(echo $var); print "The command: $cmd \n";'
Next, add system:
perl -e ' $var = "Hello"; $cmd = qq(echo $var); print "the command: $cmd \n"; system($cmd);'