It might be worth pointing out the CPAN module Data::Munge which has a function list2re to make a list-matching regex. This line is basically what you need: 

   my $re = join '|', map quotemeta, sort {length $b <=> length $a || 
+$a cmp $b } @_;

[download]

There is also this, which is what I use.

In reply to Re^3: Combining multiple =~ s/ by no longer just digit
in thread Combining multiple =~ s/ by hennesse

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