Choosing proper data structure is often key step to the solution, but first of all you should define what you are trying achieve. What is overall goal? For example I have this data file and in mine application/program I need frequently ask for this information. It is crucial to ask proper question because for example if you don't need ask frequently for keyword it doesn't make sense creating hash at all.
perl -anE'say $F[0] if $F[1] eq "Little"' FILE1.txt
Yes it is that simple. Look in perlrun
manpage for switches and what they mean and how to do same thing in bigger application.
If you need frequently ask for this question you should arrange your data in way which helps you and not in way you have to battle with.
use strict;
use warnings;
use feature qw(say);
use autodie;
open my $f, '<', 'FILE1.txt';
my %h;
while(<$f>) {
chomp;
my ($animal, $keyword) = split' ';
$h{$keyword} = $animal unless exists $h{$keyword};
}
close $f;
for my $keyword (qw(Little Awkward Small Tiny)) {
say $h{$keyword} ? "$keyword $h{$keyword}" : "keyword $keyword not found";
}
But if you still insist you want to traverse hash you can do it but you has been warned.
open my $f, '<', 'FILE1.txt';
my %h;
while (<$f>) {
chomp;
my ( $animal, $keyword ) = split ' ';
push @{ $h{$animal} }, $keyword;
}
close $f;
KEYWORD:
for my $keyword (qw(Little Awkward Small Tiny)) {
for my $animal (keys %h) {
for my $k (@{$h{$animal}}) {
if($k eq $keyword) {
say "$keyword $animal";
next KEYWORD;
}
}
}
say "keyword $keyword not found";
}