Hello guys, I've a file (with a lot of string lines of this format .*?;.*?;.*?;.*?;.*?;.*?;.*?;.*?;.*?;.*?(?:$)); I want to check those who start with the same first word after the first semicolon, then delete one of them from the file (the one that have a particular format). I write this code: 
 #!/usr/bin/perl

use warnings;

my $input = 'lines.txt';

open (FILE, "<", $input) or die "Can not open $input $!";

my @lines = <FILE>;

close FILE;

my @forlines=();

foreach(@lines){
    if( ( defined $_) and !($_ =~ /^\s*$/)){
        push(@forlines, $_);
    }
}



my @buffer = ();

foreach $line(@forlines)
    {
        $line =~/(.*?);.*?;.*?;.*?;.*?;.*?;.*?;.*?;.*?;.*?(?:$)/;
        my $var = $1;
    
        foreach $line2(@forlines)
            {        
                $line2 =~/(.*?);.*?;.*?;.*?;.*?;.*?;.*?;.*?;.*?;.*?(?:
+$)/;
            
                if ($line2 eq $line)
                    {
                        next;
                    }
                

                if($var eq $1 and $line2 =~ /(.*?);.*?;SU LI IR ST;.*?
+;SU LI IR ST;.*?;.*?;.*?;.*?;.*?(?:$)/)
                    {
                        push @buffer, $line2;
                    }
            }    
    }
    
foreach $line(@buffer)
{
    @forlines = grep {!/$line/} @forlines;
}

open(my $file, '>', $input) or die "Could not open file '$input' $!";
truncate $file,0;
print $file @forlines;

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it works but it is so slow (20 min to formating the file), I think because of the two nested loops. Is there any better solution to do that ? BR

In reply to How to check lines that start with the same word then delete one of them by agnes00

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