if statement in TCL

I have written a TCL script . There are two if loops

The below if condition is working perfectly as expected .

set flag [lindex $header 0]
if { $flag == "Rings_distance"  }  {
##do something here
}

The other if condition is as follows.

    if {  $border == "T"  }  {
    ##do something
    } elseif { $border ==  "B"  }  {
    ##do something
    } elseif { $border == "L" }  {
    ##do something
    } else  {
    ##do something
    }

The second condition is not working i m pretty sure & verified that $border is either of T/B/L...what could be the reason for this???Could you please help me debug??