Provides conditional  execution  of  a  DEBUG  command.   If  the
     language  expression  given  in  the IF clause is true, the DEBUG
     command given in the THEN clause is executed.   If  the  language
     expression  is  false,  and  an ELSE clause is present, the DEBUG
     command given in the ELSE clause is executed.

     This feature is primarily useful in DEBUG command  files  and  in
     the DO clause of breakpoints.

 Format:

     IF lang-exp THEN (debug-cmd-list) [ELSE (debug-cmd-list)]

     Example:

     DBG> SET BRE/SILENT X DO (IF Y .NE. 3 THEN (GO))
     ! The above is equivalent to:
     DBG> SET BRE/SILENT X WHEN (Y .EQ. 3)

Additional information available:

Parameters

 lang-exp

     Any expression in the currently set language which  evaluates  to
     TRUE  or  FALSE.  For example, (X .EQ.  5) in FORTRAN, or (Y[3] >
     2) in PASCAL.  See "HELP Languages *" for information  about  the
     syntax of each language.

 debug-cmd-list

     A single DEBUG command or a sequence of DEBUG commands  separated
     by semicolons.