You forgot semicolons after some statements. Anyway, in modern Perl it's written like that:

{
    open my $fh, '>', 'filename.ext';
    print $fh 'foo';
    close $fh;
};

{
    open my $fh, '<', 'filename.ext';
    while (<$fh>) {
        # $_
    };
    close $fh;
};
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