open my $fh, "<", "hard-coded-filename";
# instead of: open my $fh "<hard-coded-filename"

system qw[somecommand -o -p -q]; # hard-coded arguments
# instead of: system "somecommand -o -p -q"

##</code><code>##

join "|", map quotemeta, sort { length $b <=> length $a } keys %dict;