use strict;
use warnings;

use Test::More tests => 2;                      

my $abc  = 'dgrs';
my $n    = 1;
my $want = 'dgrs_1';
my $have = '';

$have = $abc . '_' . $n;
is $have, $want, 'Concatenation operator (perldoc perlintro)';

$have = "${abc}_$n";
is $have, $want, 'String interpolation (perldoc perlop)';