When seeking to match a series of strings like this there is no reason not to push the loop down to the RE engine. First you: 
my %service = qw(
    0050    www
    0016    ssh
    1A0B    irc
    0015    ftp
);
my $match_lst = join "|", keys %service;
my $match = qr/:($match_lst)\s/;

[download]
and then you change the loop to: 
foreach my $line (grep /\b01\s/, `cat /proc/net/tcp`  ) {
    ++$count{$service{$1}} while $line =~ /$match/g;
}

[download]
If you want you can speed it up even more by optimizing the RE as I did in RE (tilly) 4: SAS log scanner.

In reply to RE (tilly) 2: efficiency & style by tilly
in thread efficiency & style by djw

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