How do I do a LTRIM on a variable in ZPL2?

I need to trim leading spaces from a variable I'm sending to a label with ZPL2.

This is what the row of code looks like:

^FO260,39^ACR,73,25^FD$1HWWRPQT^FS

$1HWWRPQT is a variable.

I tried this:

^FO260,3^ACR,73,25^FDLTRIM$($1HWWRPQT)^FS

But it returns:

LTRIM$($1HWWRPQT)

How do I trim the variable?  Do I need something between the ^FD and the LTRIM$()?