From the POD of WWW::Mechanize:

get() is a well-behaved overloaded version of the method in LWP::UserA
+gent. This lets you do things like

    $mech->get( $url, ":content_file"=>$tempfile );
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The reference to LWP::UserAgent:

$ua->get( $url , $field_name => $value, ... )
    <snip>
    If a $filename is provided with the :content_file option, then the
+ response content will be saved here instead of in the response objec
+t.
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