Whenever "EX" instruction is there in the first column followed by 2 arguments, whatever is there in the 2nd argument will be another routine(this routine will be in the same file.). that has to be substituted in place of the entire EX statement..

Okay, so you would need 3 passes.

1. Load the file into an array line-by-line: my @file = <$fh>;
2. Scan the lines and record the routine names from the EX statements:

   my %exs;
   $file[ $_ ] =~ m[\s+EX\s+[^,]+,(\S+)] and push @{ $exs{ $1 } }, $_ for
   + 0 .. $#file;
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3. Now locate the routines referenced in the EX lines and make the substitutions:

   for my $rtn ( keys %exs ) {
       my $n = 0;
       ++$n until $file[ $n ] =~ m[$rtn\s+(\S+)];
       my $subst = $1;
       $file[ $_ ] = "\t$subst" for @{ $exs{ $rtn } };
   }
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4. Write out the modified array to a new file.

Of course, that only deals with single line substitutions; you'd need to add error checking for routines referenced but not found; and you might want to remember the lines where the substituted routines were found and remove them before output; etc. but that should get you started.

As OGB said; I can't believe that there isn't an ISPF macro to do this already in existance.