If you want, you can also expand the angle brackets into something (IM(NS)HO) more readable:

use File::Glob 'bsd_glob';

...

( $bcsdir ) = bsd_glob( "$bcsdir*" );

Note that the curly brackets around the variable name in the interpolation are only needed if what comes after the variable name might look like a longer variable name. For example, you could print it as print "$bcsdir\n";, but if you wanted to pluralize the output (in English) for some reason it would have to be print "${bcsdir}s\n";. In this extremely contrived example the curly brackets keep Perl from thinking you want to interpolate $bcsdirs.