Looping through a file to find a hash key

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

I have a hash as shown in the example below. I also have a text file with many lines of misc text. I am looking for an efficient way to loop through the file searching for any line that contains any of the keys in the hash. When one is found, I need to get the value for that hash key. I'm sure there is a better way of doing this. What am I missing?

#!/usr/bin/perl
use strict;
use warnings;

my %hash_name = (
  "one" => 1,
  "two" => 2,
  "three" => 3,
  "four" => 4
);

open MYFILE, ('/me/out.txt');
foreach my $line (<MYFILE>){
  next if grep {$_ !~ keys %hash_name} $line;
  # above line seems to work but how do I find the hash key that match
+ed?
  #  OR is there a better way to do this altogether?
}
close(MYFILE);
[download]

Comment on Looping through a file to find a hash key Download Code

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Re: Looping through a file to find a hash key by 1nickt (Canon) on Mar 03, 2016 at 00:57 UTC
Here's a very simple example showing how to use `grep` to do what you want (although that may not be the best way!): `use strict; use warnings; use feature qw/ say /; my %hash_name = ( "one" => 1, "two" => 2, "three" => 3, "four" => 4 ); while ( my $line = <DATA> ) { chomp $line; say "Line $. : $hash_name{$_}" for grep { $line =~ /$_/ } sort key +s %hash_name; } __DATA__ This one has it. This doesn't. This one has two. Nothing here. Three times lucky. Can we get a foursome for tennis? Blerghh.` [download] Output: `Line 1 : 1 Line 3 : 1 Line 3 : 2 Line 6 : 4` [download] Hope this helps! The way forward always starts with a minimal test.	[reply] [d/l] [select]
Re: Looping through a file to find a hash key ( quotemeta) by Anonymous Monk on Mar 03, 2016 at 00:19 UTC
I'm sure there is a better way of doing this. What am I missing? add `use re 'debug';` and you'll see that `keys %hash_name` doesn't make a very good pattern. You can use `my $keys = join '\|', map {"\Q$_\E"} keys %words;` but simply iterating over the has might be faster	[reply] [d/l] [select]