Building a regex that matches only that set of numbers isn't particularly hard, but it would be a huge regex and not very efficient. I'd consider doing it without a regex. Something like this perhaps:

my @list = qw(54 55 20 21 22 25) # simplifed greatly :)
my %hash;
@hash{@list} = (1) x @list;

while (<FILE>) { # assuming FILE has been opened previously
  my @row = split(/,/); # assuming comma separator

  if ($hash{$row[-1]}) {
    # process line
  }
}
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p.s. Oh, and regexen are hard because they're so powerful :)

1. They are capable of quite powerful things. Baby talk is simple, but any language used for real tasks is quite complex.
2. They are often badly taught or explained.

Nat

@numbers = map /(\d+)/g, <>;
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-- Randal L. Schwartz, Perl hacker

I am sorry. May be I should rephrase my question. These are not the only numbers in file. There are more numbers with each line. I just need to match these one and print. Thanks.

perl -ne 'if (/(\d+(\.\d+)?)$/) {print $1, "\n"}' file1 file2
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That picks up numbers at the end of the line. If you want the last number in the line (ignoring possible trailing text) throw in \D* before the $.

If you are looking to only match the numbers on the end of each line use the regex /(\d+)$/. The $ will anchor it to the end of the line for you... So getting all the numbers at the ends of the lines would be

my @numbers;
while ( <FILE> ) {
   /(\d+)$/;
   push @numbers, $1;
}
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Update: oops... As merlyn points out, don't do this.

So how do you decide whether a number is to be printed or not? Can you give a rule? Is it based on what it is, or where it is, or where it isn't?

-- Randal L. Schwartz, Perl hacker