open PIPE, "-|", "/usr/bin/tail", "-f", "$perf_logfile"
   or die "could not start 'tail' on $perf_logfile: $!";

##</code><code>##

while (<PIPE>) {
    if ( $_ =~ /(Some pattern)/i ) {
        print("- $1 encountered");
        last;
    }
}
close PIPE;