How can I see if a Perl hash already has a certain key

Question

I have a Perl script that is counting the number of occurrences of various strings in a text file  I want to be able to check if a certain string is not yet a key in the hash  Is there a better way of doing this altogether   Here is what I am doing   foreach  line   lines       if   line    m my regex                    string    1          if   string is not a key in  strings     strings  is an associative array                        strings  string    1                    else                        n     strings  string                 strings  string     n  1

User · Answer

Well  your whole code can be limited to   foreach  line   lines            strings  1    if  line    m my regex       If the value is not there     operator will assume it to be 0  and then increment to 1   If it is already there - it will simply be incremented

User · Answer

I believe to check if a key exists in a hash you just do  if  exists  strings  string               else

User · Answer

I would counsel against using if   hash  key   since it will not do what you expect if the key exists but its value is zero or empty

User · Answer

You can just go with   if   strings  string

User · Answer

I guess that this code should answer your question   use strict  use warnings   my  keys   qw one two three two   my  hash  for my  key   keys         hash  key        for my  key  keys  hash       print   key      hash  key     n       Output   three  1 one  1 two  2   The iteration can be simplified to    hash       for   keys      See    in perlvar   And you can even write something like this    hash       or print  Found new value      n  for   keys     Which reports each key the first time it   s found

[perl] How can I see if a Perl hash already has a certain key?

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