Conditionally apply or ignore prefix in search query

[Digvijay]

My code :

<search>
<query>| makeresults | eval API="party_interaction_rest" , METHOD="GET",OPERATION="Alle,LIST_PARTY_INTERACTIONS" |
append [| makeresults | eval API="ticket_mgmt_rest" , METHOD="GET",OPERATION="Alle,LIST_TROUBLE_TICKETS"] | eval OPERATION=split(OPERATION,",")
|mvexpand OPERATION| table API METHOD OPERATION | search API="$token_service$" METHOD =$token_method$ </query>
</search>

In above code $token_method$ is dropdown field for which prefix is defined  as below:

<input type="dropdown" token="token_method" searchWhenChanged="true">
<label>Select Method:</label>
<fieldForLabel>METHOD</fieldForLabel>
<fieldForValue>METHOD</fieldForValue>
<search>
<query>| makeresults | eval API="party_interaction_rest",METHOD="Alle,GET,POST" |
append [| makeresults | eval API="ticket_mgmt_rest",METHOD="Alle,GET,POST,PATCH"] |
append [| makeresults | eval API="customer_management_rest",METHOD="Alle,GET,PATCH"] |
append [| makeresults | eval API="agreement_management_rest",METHOD="Alle,GET"] |
append [| makeresults | eval API="product_order_rest",METHOD="Alle,GET,POST,PATCH,DELETE"] |
append [| makeresults | eval API="cust_comm_rest",METHOD="Alle,GET"] |
append [| makeresults | eval API="product_inv_rest",METHOD="Alle,GET,POST,PATCH"] | eval METHOD=split(METHOD,",")
|mvexpand METHOD| table API METHOD | search API="$token_service$"</query>
</search>
<change>
<condition value="Alle">
<set token="token_method">*</set>
</condition>
</change>
<default>Alle</default>
<prefix>"properties.httpMethod"=</prefix>
<initialValue>Alle</initialValue>
</input>

So I want to ignore prefix in some case and only need value from dropdown but in some cases I need prefix .Please guide.