Example just teaking your code slightly:

use strict;
use warnings;
open (MER, "Extracted.c") or die "Can't open input file. $!\n";
my %cases;
for my $mer(<Mer>){
    my $control;
    while ($control!=15){
        $mer =~ s/ //; 
        $control++;
    }
    $cases{$mer}++;
}
foreach $key ( keys %cases ) {
    print $key, "\n";
}
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I'm not really clear on that the inner loop is for. You only want to remove the first fifteen spaces from $mer? ...ok. I guess that's working out ok. You could alternatively use something like:

substr($mer,0,15) =~ s/ //g;

That would eliminate the while loop and $control counter.

hi,
thanks for your advice, i have got it to work. by the way, the while loop is to help me align the list to the left as there are some spaces in front. your code really helps!!!
a thousand thanks!!!
Levan

The usual way of removing duplicates from a list is to form a hash. Instead of printing in line 8,     $fnames{$mer} = ''; Then you can extract sort keys %fname to be printed, or for whatever other use you have.

open (Mer, "Extracted.c")
%vars;
for $mer(<Mer>){
  $control=0;
  while ($control!=15){
    $mer =~ s/ //; 
    $control++;
  }
  $vars{$mer} = 1;
}
print "$_" foreach(keys %vars);
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open (Mer, "Extracted.c")
%vars;
for $mer(<Mer>){
  $control=0;
  while ($control!=15){
    $mer =~ s/ //; 
    $control++;
  }
  next if $vars{$mer};
  $vars{$mer} = 1;
  print $mer;
}
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use strict;
use IO::File;
my $Mer = new IO::File "Extracted.c", "r"
  or die "Can not open file!";
my %vars;
while my $mer (<$Mer>) {
...
}
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That last statement is pretty odd. open() has had new enhancements in just about every perl release... why would that happen if it were deprecated?

Try to use IO::File to open a file in perl. It's the preferred method. ;-)

It is? It may be one method but I don't think it's the preferred method.

-- vek --

perl my_script.pl | uniq
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Correction:

perl my_script.pl | sort | uniq
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uniq will only work if the items are sorted (or at least if all of the identical items are consecutive).

$ printf "a\nb\na\n" |uniq
a
b
a

sort |uniq would work, though, or sort -u.

thor

my $list = 
"RcvChar
checkeof
SerialOutputString
SerialOutputString
SerialOutputString
GetFile
ChksumByteByByte
GetChksum
SerialOutputString
SerialOutputString";
while ($list =~ s/(\b\w+\b)(.*?)\s+\1\b/$1$2/s) {};
print $list;
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RcvChar
checkeof
SerialOutputString
GetFile
ChksumByteByByte
GetChksum
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You've received some good suggestions from other monks so I just had a couple of comments about your code.

open (Mer, "Extracted.c");
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Always try and get in the habit of checking the return value of open:

open (MER, "Extracted.c") || 
   die "open: Extracted.c - $!\n";
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Your for looks a little out of place for processing each line in the file. I dunno, whatever floats your boat I suppose but I think you'll probably see most people use a while loop:

while (<MER>) {
   # do stuff
}
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hi,
actually the codes that i have put up is a shorter version of what i actually had. Cos i think the codes are a bit too long and complicated to be put up on this thread, so i shorted it. thanks for the advice!!!
Levan