++ for "Close!" ...but "untested" lets typos slip by:

open (LOGFILE, "<$file") or die "Can't open $file";
my @lines = <LOGFILE>;
my $lines; my $i;
for $i(0..$#lines) {
    next unless $lines[$i] =~ /$string_to_find/i;
      my $a = $i - 5 < 0 ? 0 : $i - 5;;
    my $b = $i + 5 > $#lines ? $#lines : $i + 5;
    for $i($a..$b) {
        print $lines[$i];
    }
}
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