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 spa
+ces
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;
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Update 1: In example B or C above, what happens if the {} curly braces are left out of the "${abc}_$_" expression, so it becomes "$abc_$_"? Try it! Do you get the desired or expected result? If not, why not?

Update 2: Examples of 1nickt's approach++ and one other. Note that the concern about curly braces goes away.

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;
[download]