open's first argument can be a reference to a filehandle. As of perl 5.6.0, if the argument is uninitialized, Perl will automatically create a filehandle and put a reference to it in the first argument, like so:

    open( my $in, $infile )   or die "Couldn't read $infile: $!";
    while ( <$in> ) {
    # do something with $_
    }
    close $in;
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Indirect filehandles make namespace management easier. Since filehandles are global to the current package, two subroutines trying to open INFILE will clash. With two functions opening indirect filehandles like my $infile, there's no clash and no need to worry about future conflicts. Another convenient behavior is that an indirect filehandle automatically closes when it goes out of scope or when you undefine it:

    sub firstline {
    open( my $in, shift ) && return scalar <$in>;
    # no close() required
    }
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bind_param

  $sth->bind_param($p_num, $bind_value)
  $sth->bind_param($p_num, $bind_value, \%attr)
  $sth->bind_param($p_num, $bind_value, $bind_type)
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The bind_param method takes a copy of $bind_value and associates it (binds it) with a placeholder, identified by $p_num, embedded in the prepared statement. Placeholders are indicated with question mark character (?). For example:

  $dbh->{RaiseError} = 1;        # save having to check each method ca
+ll
  $sth = $dbh->prepare("SELECT name, age FROM people WHERE name LIKE ?
+");
  $sth->bind_param(1, "John%");  # placeholders are numbered from 1
  $sth->execute;
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