Win8 Strawberry 5.8.9.5 (32)  Tue 03/16/2021 21:10:53
C:\@Work\Perl\monks
>perl -Mstrict -Mwarnings

my $abc = 'dgrs';
$_ = 1;

# print $temp_out "$abc . _$_;\n";  # not this, with extra dot and spaces
print 'A: ', $abc . "_$_", "\n";    # but this ...
print 'B: ', "${abc}_$_", "\n";     # or this.
print "C: ${abc}_$_;\n";            # update: or even this.

^Z
A: dgrs_1
B: dgrs_1
C: dgrs_1;

##</code><code>##

Win8 Strawberry 5.8.9.5 (32)  Tue 03/16/2021 23:02:15
C:\@Work\Perl\monks
>perl -Mstrict -Mwarnings

my $abc = 'dgrs';
$_ = 1;

printf "D: %s_%d;\n", $abc, $_;

my $spf = sprintf "E: %s_%d;\n", $abc, $_;
print $spf;

my $fmt_dgrs = "F: %s_%d;\n";
printf $fmt_dgrs, $abc, $_;

print join '', 'G: ', $abc, '_', $_, ';', "\n"

^Z
D: dgrs_1;
E: dgrs_1;
F: dgrs_1;
G: dgrs_1;