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if ($read) {
  if ($more) {
    # do something
  }
}

#!/usr/bin/perl -w

#or
use warnings;

foreach $line (@File_pre_format) {
  $file_pre_format .= $line;
}
...
$file_pre_format =~ s/\n|\t//g;
# or in this simple case even better:
$file_pre_format =~ tr/\n\t//d;