while (<INFILE>) {
  $word = <STDIN>;
  print if /$word/;
}

# Officiate is asked for input on every line of the file.
# Officiate throttles monk; blacking out, you meditate on your error.

##</code><code>##

while (<INFILE>) {
  $line = $_;
}
my $word = <STDIN>;
print $line if $line =~ /$word/;

# $line only contains the last line of the file!
# Officiate makes bad decision based on wrong output.
# Monk goes hungry.

##</code><code>##

while (<INFILE>) {
  push @lines, $_;
}
$word = <STDIN>;
foreach (@lines) {
  print if /$word/;
}

# File data is stored until $word is known.
# Officiate gets correct output, is pleased while file is small.
# Monk is thrashed when the disk thrashes on a large file.

##</code><code>##

$word = <STDIN>;
while (<INFILE>) {
  print if /$word/;
}

# There is no need to store the file data.
# Harmony is achieved.

##</code><code>##

#!/usr/bin/perl -W
use warnings 'all';
use strict;
# Scans the input file(s), breaking each line into fields. 
# Builds a key from prettified $type, and stores an array of 
# output lines in a hash under the key. Prints a list of all 
# the types seen in the file(s), and asks the user to choose one.
# Prints the output lines stored for that key/type.

my $limit = 30;
my $usage = "Usage: $0 infile\n";
die $usage unless @ARGV;

sub pretty { return ucfirst lc shift }

my %lines;
while (<>) {
  my ($whatever, $type, $num) = split;
  my $key = pretty($type);
  push @{ $lines{$key} }, "$type\t$num\n" if $num < $limit;
}

my @types = sort keys %lines;

my $ask = "Please select a category:\n";
$ask .= "\t$_. $types[$_]\n" foreach 0 .. $#types;

my $type;
while (not $type) {
  print $ask;
  chomp(my $choice = <STDIN>);
  $type = $types[$choice] or print "$choice was not an option!\n" and next;
}
my $key = pretty($type);
print @{ $lines{$key} };