Categorise Columns by initials

[#1]

I'm trying to list available categories of columns based on the first 3 letters of the column title.  I can list all the available values readily but I have many duplicates.  Summarize doesn't obviously work for anything but a list of columns and what I have is a list of initials.  I tried this with no luck.  Any help appreciated.

dt = Current Data Table();
dt << Clear Column Selection();

colList = dt << get column names( string );

found_list={};

For( i = 1, i >= N Items( collist ), i++, 

Spud = Char(Munger( Head Name( As Namespace( colList[i] ) ), 0, 3 ));

	If( !Contains(found_list), Spud, insert into(found_list, Spud ))

);

Show(found_list);

[#2 · Accepted solution]

Does this get you any further along

names default to here(1);
dt =
// Open Data Table: semiconductor capability.jmp
// → Data Table( "semiconductor capability" )
Open( "$SAMPLE_DATA/semiconductor capability.jmp" );

colList = dt << get column names( string );

for each({col,index}, colList,
	colList[index] = substr(col,1,3)
)

grps = associative array(colList)<<get keys;

It returns all of the unique 3 letter names

[#3]

Thanks Jim.  There's a ; missing but works well.