http://www.perlmonks.org?node_id=686308


in reply to Re^3: Generate a truth table from input string
in thread Generate a truth table from input string

or as use warnings; would say...
\1 better written as $1

and use diagnostics; would elaborate...

(W syntax) Outside of patterns, backreferences live on as variable +s. The use of backslashes is grandfathered on the right-hand side of +a substitution, but stylistically it's better to use the variable fo +rm because other Perl programmers will expect it, and it works better + if there are more than 9 backreferences.