Something

     for {set i 0} {$i < [llength $signals]} {incr i} {
         set signal [lindex $signals $i]
#check the signal
         if {$signal == something} {
              lreplace $signals $i $i
          } 
}



set idx -1
		foreach val $list {
		   incr idx
		   if {"$val is to be removed"} {
		      set list [lreplace $list $idx $idx]
		      incr idx -1
		   }
		}