How to strip the last char from a string in the DTL

When using $EXTRACT, you use a * to signify an offset from the end of a string. So if you did $EXTRACT(Str,1,*-1) you would have the string with the last character removed.

Also note that the arguments for the $EXTRACT are the string, the starting character, and the ending character, so in the examples you gave, you're actually telling it to extract from Str starting at Length(Str)-1. You need to have a 1 in there as the second argument to go from the beginning to that character.

@Sreevani Goli - if you know it is comma delimited and you want to strip off the last comma, you could use $piece() as follows:

USER>s Str="Addr1,Addr2,"
 
USER>write $piece(Str,",",1,*-1)
Addr1,Addr2

This will basically grab the entire string except for the last comma (and anything that comes after it).  

In general, $extract() and $zstrip() are your friends.
If you want to strip ONLY the LAST character, then use this

set data="abc,,"
set $extract(data,*)=""
write data --> abc,

If you want to strip ALL (same) trailing characters, use this

set remove=","
set data1="abc,"
set data2="abc,,,"
set data3="abc,,-,,"
set data1=$zstrip(data1,">",remove)
set data2=$zstrip(data2,">",remove)
set data3=$zstrip(data3,">",remove)

write data1 --> abc
write data2 --> abc
write data3 --> abc,,-