Three suggestions spring to mind for combining the print statements, you could either combine the tests into one regular expression:

print "$_" if /\b12345\b|
               \b12346\b|
               \b20034\b|
               \b8787\b|
               \b31337\b|
               \b31338\b|
               \b54320\b|
               \b54321\b/x;
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or combine the different regular expressions into one logical test:

print "$_" if (/\b12345\b/ or
               /\b12346\b/ or
               /\b20034\b/ or
               /\b8787\b/ or
               /\b31337\b/ or
               /\b31338\b/ or
               /\b54320\b/ or
               /\b54321\b/);
[download]

or use a little loop:

my @ports = map { qr/$_/ } ("\b12345\b", "\b12346\b", "\b20034\b",
                            "\b8787\b", "\b31337\b", "\b31338\b",
                            "\b54320\b", "\b54321\b");
while (<FWLOG>) {
    for my $port (@ports) {
        if ($_ =~ $port) {
            print;
            last;
        }
    }
}
[download]

(This idea for the last one was pinched from jcwren, implementation pinched from various others).

Nuance