Re: getting wrong value

And you are not calling the function

 open(INFILE, '<','test.dat');   
 open(OUTFILE, '>','hex.dat');   
 while(<INFILE>){                                
  chomp;  
  #printf ("%#x", $line) > $line2; 
  my $line2 = &capture_stdout($_) ; ### <--- see the &
  print OUTFILE $line2,"\n";   
  }                                
                                   
      sub capture_stdout(){                                
         my $v;                        
         local *STDOUT;                 
         open(STDOUT, '>', \$v);        
         printf ("%#x", $_);          
         return $v;                     
     }                                
 
close INFILE;                              
close OUTFILE;
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In any case you can use pack for this, probably

In Section Seekers of Perl Wisdom