You need to use braces as you have with the other variables to detach the trailing underscore from the variable name.

use strict;
use warnings;

my $opstr = '01';
my $foo = "a_${opstr}_b";
print "$foo\n";

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If you remove the braces even this short snippet will not compile.

🦛

In reply to Re: appending a variable by hippo
in thread appending a variable by pragovnj

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