How I can avoid that .

Open the file in  >> append mode:

c:\@Work\Perl\junque>perl -wMstrict -e
"my $file = 'junk';
 for my $s (qw(foo bar baz)) {
   open my $fh, '>>', $file    or die qq{opening '$file': $!};
   print $fh qq{this is $s \n} or die qq{writing '$file': $!};
   close $fh                   or die qq{closing '$file': $!};
   }
"

c:\@Work\Perl\junque>cat junk
this is foo
this is bar
this is baz
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