--- a/table-union.xml	Fri Mar 09 11:14:02 2018 -0500
+++ b/table-union.xml	Tue Oct 30 16:18:02 2018 -0400
@@ -4,14 +4,32 @@
         <!-- <requirement type="package" version="3.4">python</requirement> -->
     </requirements>
     <command detect_errors="exit_code"><![CDATA[
-        python $__tool_directory__/table-union.py 
+    	#if $input_type.source_select == 'two'
+    	#set tables=($table_1, $table_2)
+    	#else
+    	#set tables=$input_type.tables
+    	#end if
+        python $__tool_directory__/table-union.py "$union"
         #for $table in $tables
             $table
         #end for
         > $combined_table
     ]]></command>
     <inputs>
-        <param name="tables" type="data_collection" format="tsv" collection_type="list" />
+    	<param name="union" type="boolean" label="Attempt to unionize on an autodetected key column" checked="false" falsevalue="" />
+    	<conditional name="input_type">
+    		<param name="source_select" type="select" label="Mode">
+    			<option value="two">Combine two tables</option>
+    			<option value="collection">Combine a collection of tables</option>
+    		</param>
+    		<when value="collection">
+       			<param name="tables" type="data_collection" format="tabular,tsv" collection_type="list" />
+       		</when>
+       		<when value="two">
+       			<param name="table_1" type="data" format="tabular,tsv" />
+       			<param name="table_2" type="data" format="tabular,tsv" />
+       		</when>
+        </conditional>
     </inputs>
     <outputs>
         <data name="combined_table" format="tsv" label="Combined table" />
@@ -19,6 +37,8 @@
 
     <tests>
         <test>
+        	<param name="source_select" value="collection" />
+        	<param name="union" value="true" />
             <param name="tables">
                 <collection type="list">
                     <element name="1" value="dingbat.tsv" />
@@ -27,6 +47,13 @@
             </param>
             <output name="combined_table" value="combined.tsv" />
         </test>
+        <test>
+        	<param name="source_select" value="two" />
+        	<param name="union" value="false" />
+        	<param name="table_1" value="dingbat.tsv" />
+        	<param name="table_2" value="loki.tsv" />
+        	<output name="combined_table" value="no_union.tsv" />
+        </test>
     </tests>
     <help><![CDATA[
         Concatenate a collection of TSV files wile preserving and unionizing headers.