if the file isn't big, read it all in an array, then when you find your match, save your location, and retrieve it directly from the array..

Update:Here it is, completely untested for bugs:

# assuming the file is already opened and has a <IN> filehandle

my @temp;

# and assuming that you won't match before the first 5 lines..

while (my $line = <IN>) {
    push @temp, $line;
    shift @temp if (scalar @temp > 5);
    if ($line =~ /foo/) { 
        # we've got a match.
        print $temp[0];
    }
}
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Update 2: This looks like davorg's more elegant solution.