Pattern matching can also be used to manipulate
variables. In particular, many CGI scripts take
advantage of the "=~" operator in conjunction with the
substitution operator using the format
$variable_name =~
s/[string_to_remove]/[string_to_add]/gi;
For example, if we want to censor every occurrence of
the word "Frack" from the client-defined input field
"comment", we might use the line
$form_data{'comments'} =~ s/frack/censored/gi;
