Regex to match Perl package syntax

demo.pl

#!/home/ben/software/install/bin/perl
use warnings;
use strict;
use utf8;
use FindBin '$Bin';
use Test::More;
my @stuff;
# package NAMESPACE
$stuff[0] =<<EOF;
package switch;
EOF
# package NAMESPACE VERSION
$stuff[1] =<<EOF;
package switch 0.001;
EOF
# package NAMESPACE BLOCK
$stuff[2] =<<EOF;
package switch
{ }
EOF
# package NAMESPACE VERSION BLOCK
$stuff[3] =<<EOF;
package switch 0.001
{ }
EOF

my $gokeyw =<<EOF;
break        default      func         interface    select
case         defer        go           map          struct
chan         else         goto         package      switch
const        fallthrough  if           range        type
continue     for          import       return       var
EOF

my $re = qr!package\s+.*?\s*(;|\{)!;

for (@stuff) {
    ok (m!$re!);
}
ok ($gokeyw !~ m!$re!);
done_testing ();