Extract pattern from file

gistfile1.pl

#!/usr/bin/perl
##############################################################################
#       $fileName : a filename to analyze
#       $pattern : regexp pattern
#       $patternIndex : a group index to extract(0..n)
#       (OPT)$count : count will be printed if value is 1
##############################################################################
 
if (@ARGV < 2) {
  print("usage : $0 (M)FILE_NAME (M)PATTERN\n");
  exit 1;
}
 
my $fileName = $ARGV[0];
my $pattern = $ARGV[1];
my $patternIndex = $ARGV[2];
$pattern = "(".$pattern.")" unless ($pattern =~ /\(.*\)/);
my $count = $ARGV[3] eq "" ? "0" : $ARGV[3];
 
open(FH, "$fileName") or die("Failed to open the file '$fileName'.");
while($line = <FH>) {
  chomp($line);
  my @str = ($line =~ /$pattern/);
  my $value = $str[$patternIndex];
  if ($nos{$value} eq "") {
    $nos{$value} = "1";
  } else {
    $nos{$value} = $nos{$value} + 1;
  }
}
 
for my $key (sort keys %nos) {
  print("'$key'\t$nos{$key}\n") if ($count == 1);
  print("$key\n") if ($count == 0);
}
 
close FH;