This works very well, thank all of you for your help.

Where can I place a print statement that seperates the output results for each match?

#!/Perl/bin/perl -w

open(INFILE, "< file.log")
         or die "Cant open file : $!";

open(OUT, "> results.txt")
         or die "Cant open new file : $!";

use strict;
my $pattern = "Error while detecting new item";
my @history = ("\n") x 3;
while (<INFILE>) {
print OUT @history if /$pattern/;
    push @history, $_;
    shift @history;
}

print $.;
close INFILE;
close OUT;
exit;
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Example:

results.txt
matched line 1
matched line 2
matched line 3
results of first match
matched line 1
matched line 2
matched line 3
results of second match
and so on...
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Thank you again so much, Neurotoxx

What does the '' vs. "\n" do?

How could I print also the same line that has the pattern match?

Thank you Sifu,<\p>

Neurotoxx

Print the empty string prints nothing. Printing a newline prints an empty line.

my @history = ('') x 3;
while (<>) {
    print @history, $_ if /pattern/;
    push @history, $_;
    shift @history;
}
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or

my @history = ('') x 4;
while (<>) {
    push @history, $_;
    shift @history;
    print @history, $_ if /pattern/;
}
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Thank you very much for your help.

I'm sorry to bother, but how can I add the existing matched line with the three lines?

++, but that should be my @history = ('') x 3;
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++, but that should be my @history = ('') x 3 + $.; #???
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Thank you agian.

Already asked. Alread answered

Figured it out...to add the line that contains the match string, I added an additional line to the loop. Probably not the best way, but it works.

while (<$_>) {
print OUT @history if /$pattern/;
print OUT $_ if /$pattern/; # adds line with match
push @history, $_;
shift @history;
        }
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Thanks again every one,

Neurotoxx