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#!/usr/bin/perl -w                                                    
+                           
use strict;
...
    print "$data{$pos} $pos\n" if $data{$pos};
}
close (B);

Error: 
Use of uninitialized value $pos in hash element at ./second_str_map.pl
+ line 29, <B> line 298.
...
Use of uninitialized value $pos in hash element at ./second_str_map.pl
+ line 29, <B> line 300.
Use of uninitialized value $_ in split at ./second_str_map.pl line 28,
+ <B> line 301.
Use of uninitialized value $pos in hash element at ./second_str_map.pl
+ line 29, <B> line 301.