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while (<>) {
    # do something with $_ here
}

unshift(@ARGV, '-') unless @ARGV;
while ($ARGV = shift) {
...
        # do something with $_
    }
}

%hash = ();
{
...
        $hash { $keys [$c] } = $values [ $c ];
    }
}

@hash { qw (a, b, c) } = 1..3;

{ # block for local
    local $/ = ''; # paragraph mode
...
        } # end of sub
    );
} # end of "local $/" block