One option is to use regex, it has a pretty steep learning curve but is very powerful:
Regex( :Original Column, "sgl", "Sgl", IGNORECASE, GLOBALREPLACE )
Here is an example table:
New Table( "Replace Example",
Add Rows( 3 ),
New Column( "Original", Character, "Nominal", Set Values( {"sglLrg500", "sglLrg800", "sglLrg150"} ) ),
New Column( "Clean",
Character,
"Nominal",
Formula( Regex( :Original, "sgl", "Sgl", IGNORECASE, GLOBALREPLACE ) ),
Set Selected,
Set Display Width( 72 )
)
)