Please use \S+ instead of .*? so that backtracking won't waste CPU time. Please include \s after ($DEST_PORT) so that you won't match just a prefix of the destination port number.

I'd add to the above what perlguy recommended: 

my %r= (
    source_addr => '\S+',
    dest_addr   => '\S+',
    proto       => '\S+',
    source_port => '\d+',
    dest_port   => '\d+',
);
for my $param (  keys %r  ) {
    my $value= $cgi->param($param) || "";
    if(  $value =~ s/^!\s*//  ) {
        $r{$param}= "(?!\Q$value\E\s)($r{$param})";
    } elsif(  $value  =~ /\S/  ) {
        $r{$param}= "(\Q$value\E)";
    } else {
        $r{$param}= "($r{$param})";
    }
}

my $regex= qr/
    ^
    \d+\s+
    (\d+)\s+
    $r{source_addr}\s+
    ->\s+
    $r{$dest_addr}\s+
    $r{$proto}\s+
    $r{$source_port}
    \s+>\s+
    $r{$dest_port}\s+
/x;

while(  my $pkt= <DATA>  ) {
    print $pkt   if  $pkt =~ $regex;
}

[download]

                - tye

In reply to Re^2: Runtime Regexp Generation (! .*?) by tye
in thread Runtime Regexp Generation by tekkie

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