DBI, s/// => unitinitialized value in substitution

brwarn has asked for the wisdom of the Perl Monks concerning the following question:

Hello Monks, I can't figure out what to do with my s/// line below to get rid of the 'uninitialized value in substitution' error that I'm getting. I looked at this earlier thread for some insight, but can't figure out how to apply it to my case. Anyway, the offending code is:

# initialize @row
my @row;
# for each table row, apply all the regex patterns in order to the tva
+l_test column
    open(FILE, "< $file") || die "Can't open regex.txt: $!\n";
        while(my $regex=<FILE>){
            # get all tval_test columns
            my $sql_q = "select tval_test from cas_testbed.rtemp";
            my $sthr = $dbh->prepare($sql_q);
            $sthr->execute;            
            my @rex = split(/\s/,$regex);  
            # work on each tval_test row
            while (@row = $sthr->fetchrow_array){
                # search for $rex[0] and replace with $rex[1]
                s/$rex[0]/$rex[1]/ig;
            } # END while (@row = $sth->fetchrow_array)
            $sthr->finish;
        } # END while(my $regex=<FILE>)
    close FILE;
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Re: DBI, s/// => unitinitialized value in substitution by bellaire (Hermit) on Mar 05, 2009 at 17:07 UTC
I don't see where `@rex` is being initialized. Did you mean to use `$row[]` instead? That would certainly explain the uninitialized value warning. Update: Actually, you're subtituting on $_, which isn't being set either. I think your code sample is incomplete!	[reply]
Re: DBI, s/// => unitinitialized value in substitution by kennethk (Abbot) on Mar 05, 2009 at 17:08 UTC
The earlier thread includes the answer. In addition, you never initialize @rex, and thus never initialize either your match or replacement expressions.	[reply]
Re: DBI, s/// => unitinitialized value in substitution by swampyankee (Parson) on Mar 05, 2009 at 17:08 UTC
Always use warnings and use strict; they will prevent many bad surprises. Using this you'd probably notice that `@rex` doesn't seem to have been set. Information about American English usage here and here. Floating point issues? Please read this before posting. — emc	[reply]
SOLVED: DBI, s/// => unitinitialized value in substitution by brwarn (Novice) on Mar 05, 2009 at 18:13 UTC
Thanks everyone. I did need as noted to initialize $_ to get s/// to work. I actually had initialized @rex, but inadvertently deleted it in my original post. Thanks again!	[reply]
Re: DBI, s/// => unitinitialized value in substitution by moritz (Cardinal) on Mar 05, 2009 at 17:07 UTC
Where does `@rex` come from? Did you mean `@row`? Even if so, you're only selecting one value from the table, so `$row[1]` will always be uninitialized. And always remember to `use strict;`	[reply] [d/l] [select]
Re: DBI, s/// => unitinitialized value in substitution by locked_user sundialsvc4 (Abbot) on Mar 05, 2009 at 19:17 UTC
I suggest that you re-code the statement to remove all doubt ... to eliminate any possible uncertainty about what those square-brackets might mean. `my $foo = $rex[0]; my $bar = $rex[1]; s/$foo/$bar/ig;` [download] Realistically, it won't make any difference to the Perl compiler, and now “the designer's intentions are made clear.”