The other alternative to spelling out the concatenation is to use Perl's provisions for disambiguating the variable name (which is why the OP split up the concatenation): 
my $file = "/usr/local/apache2/htdocs/crs_desc/${course_no}desc.txt";

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Makeshifts last the longest.

In reply to Re^2: Concantenation (variable name disambiguation) by Aristotle
in thread Concantenation by chriso

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