Re GrandFather's ( ++ )

my $find = qr'license @abc';

versus

my $find = qr/license \@abc/;

see perldoc perlop at " Quote and Quote-like Operators" re the quoting ( ww added notes marked by "<!--"):

While we usually think of quotes as literal values, in Perl they function as operators, providing various kinds of interpolating and pattern matching capabilities. Perl provides customary quote characters for these behaviors, but also provides a way for you to choose your quote character for any of them. In the following table, a "{}" represents any pair of delimiters you choose.

Customary  Generic        Meaning        Interpolates
     ''       q{}          Literal             no
     ""      qq{}          Literal             yes
     ``      qx{}          Command             yes*
             qw{}         Word list            no
     //       m{}       Pattern match          yes*
             qr{}          Pattern             yes*     <!-- backslash is required 
                                                             if using /.../ 
             s{}{}       Substitution          yes* 
     ....
     * unless the delimiter is ''.                      <!-- NB!

In other words, if you chose to use my $find = qr/license \@abc/;, the escaping backwhack is required (as massa advised AND as you would have learned had you used the strictures recommended above).