Assuming "on either side" to mean "on both sides" (see my post above), try this awfully ugly code:

use strict;
use warnings;
my $ariths = quotemeta '()+</*><-';
while ( <DATA> ) {
   s/(?:(?:(?<=[$ariths])BAD)|^BAD)(?=[$ariths])/HELL/g;
   print;
}

__DATA__
+BAD        # No
BAD/       # Yes
BAD)       # Yes
(BAD<)     # Yes
BAD         # No
BADGER      # No
BADGER+     # No
+SINBAD+    # No      
BAD (BAD+  # No then Yes

[download]

Improvements welcome!

dave

Update: davido's corrected regex above already represents a significant improvement!

In reply to Re: string substitution by Not_a_Number
in thread string substitution by Anonymous Monk

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