use PPR;
my $perl_code = <<'END';
#!/usr/bin/env perl
use warnings;
use strict;
print "Hello, World!\n";
END
if ( $perl_code =~ m{ \A (?&PerlDocument) \Z $PPR::GRAMMAR }x )
     { print "It looks like it could parse as Perl\n" }
else { print "It doesn't look like Perl\n" }