Twice you do something like this:

   foreach(@array){
      my $item = $_;
      ...
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The common way is just for my $item (@array) {.

Or take advantage of the default loop variable, $_. For example, this:

   foreach(@attchfiles) {   
       my $attchfilename = $_;   
       $attchfilename =~ tr/A-Z/a-z/;    
       rename($_, $attchfilename); 
    }
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Could be simplified as:

   rename($_,lc) for @attchfiles;
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But, you should probably make sure the lowercase file doesn't already exist. Perhaps like so:

   for(@attchfiles){
      if ( -e lc ) {
         # do something appropriate!
      } else {
         rename $_,lc;
      }
   }
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