• perldoc -f grep
• perldoc perlretut

What have you tried? How did it fail? What messages (errors and/or warnings) did your code produce?

Oh, you do know, don't you, that this isn't a free coding service? We try to help those who help themselves. See also On asking for help (and not just "by the way," Markup in the Monastery or, at least, the directions surrounding the text-input box where you created your node).

In addition to what ww asked, why do you "have to do it in a [P]erl script"? If I were to pick a program to accomplish your task, I'd use grep.

This answer is a bit rushed as I'm in a hurry to go home for a beer, but you should get the idea.

# slurp the file....
my @lines = <$fh>;
# filter the lines....
my @filter1 = grep( /mixed/, @lines);
my @filter2 = grep( !/-- --/,@filter1);
[download]

## cat p.pl ; perl p.pl

#  This is "grep -f" like.

use v5.10.0; use strict;

my @in =
  ( "polka\n"
  , "avoid redding dot me\n"
  , "dot me\n"
  , "yellow\n"
  );
my $find  = 'me';
my $avoid = 'avoid';

for my $ignore ( $avoid , undef )
{
  process_input( $find , $ignore , @in );
  print "- - - -\n";
}
exit;


sub process_input
{
  my ( $grep , $skip , @in ) = @_;

  my $show;
  while ( my $line = shift @in )
  {
    $show =
      find( $grep , $line )
      &&
      ( defined $skip ? ! find ( $skip , $line ) : 1 )
      ;
  }
  continue
  {
    $show and print $line;
  }

  return;
}

sub find
{
  my ( $find , $line ) = @_;

  defined $find && defined $line
    or return;

  my @break = split '' , $find;
  my $size  = scalar @break;

  my $start = 0;
  my ( @seen );
  for my $c ( @break )
  {
    my $i = index $line , $c , $start;

    $i == -1 || scalar @seen == $size
      and last;

    push @seen , $i;

    if ( scalar @seen > 1 )
    {
      $seen[-1] - $seen[-2] == 1 or last;
    }

    $start = $i + 1;
  }

  return scalar @seen == $size
}

__END__
dot me
- - - -
avoid redding dot me
dot me
- - - -
[download]

I had made a grave error when I declared ...

...
#  This is "grep -f" like.
...
[download]

... for there was nothing of that sort. I should have just written fgrep instead of futzing with option name to indicate grep to run in fixed string search mode. To repent, comment should have been ...

...
#  This partially tested program has limited
#  fgrep-like behaviour. 
...
[download]

abcd dg 17786 sam mixed --

abcd -- 17889 ram -- --

dg 17786 dam mixed --