grep every other occurrence of a value

I have an output file with multiple occurrences of a value. E.g.:

value 123  
value 111  
value 456  
value 111  
value 789  
value 111

If I use the following command, I can print all the occurrences of 'value':

grep 'value ' file_name

But I only want to print every other occurrence. Is there some way that I can edit my command to do this?

Solution

Use this Perl one-liner to filter the results of grep:

grep 'value' file_name | perl -ne 'print if $. % 2;'

The Perl one-liner uses these command line flags:
-e : Tells Perl to look for code in-line, instead of in a file.
-n : Loop over the input one line at a time, assigning it to $_ by default.

$. : Current input line number.