"Only `perl` can parse Perl"

People are fond of saying this
If you want to know what Perl will think of some program, you must ask perl itself
No regex or other simple process will always produce the right answer
This is because to parse Perl, you also have to be able to interpret Perl
Bizarre but typical example:

        $t = time / 3;          # Is this a comment? /;

        $s =  sin / 3;          # Is this a comment? /;

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"Only perl can parse Perl"