#!/ust/bin/perl
use strict;
use warnings;

my $file='./test.txt';

open (my $in, '+<', $file) or die("ERROR OPEN $file ($!)\n");
while(<$in>)
{
  if(/TESTWORT1/ .. /---/)
  {
    print "TESTWORT1 found\n";
    seek($in, 0,0);
    truncate($in,0);
  }
  else
  {
    print "TESTWORT1 not found\n";
  }
}
close($in);
print "EXIT\n";