How to distinguish between "0" and NULL in perl? -

here looking string "reftext" in given file. line next contains string 3 integers. extracting them in @all_num. printing value of @all_num[2] if not null. logic used here doesn't print @all_num[2] if has 0.

#!/usr/bin/perl open( readfile, "<myfile.txt" ); @list        = <readfile>; $total_lines = scalar @list;  ( $count = 0; $count < $total_lines; $count++ ) {     if (@list[ $count =~ /reftext/ )         {             @all_num = @list[ $count + 1 ] =~ /(\d+)/g;             if ( @all_num[2] != null ) {                 print "@all_num[2]\n";             }     } } 

perl not include null, line

if(@all_num[2]!= null) 

is nonsensical in perl. (more accurately, attempts locate sub named null , run value compare against @all_num[2], fails because (presumably) haven't defined such sub.) note that, if had enabled use strict, cause fatal error instead of pretending work. 1 of many reasons always use strict.

side note: when pull value out of array, it's single value, should $all_num[2] rather @all_num[2] when referring third element of array @all_num. (yes, little confusing used to. hear it's been changed in perl 6, i'm assuming you're using perl 5 here.) note that, if had enabled use warnings, have told "scalar value @all_num[2] better written $all_num[2]". 1 of many reasons always use warnings.

if want test whether $all_num[2] contains value, proper way express in perl is

if (defined $all_num[2])