You grep expression is in the form:grep EXPR,LIST. But EXPR is fixed as $var1 - not a regexp or code block.

grep will return the whole list or an empty list depending on whether $var evaluates to true or false. Consider:

my @arr1 = ('a');

foreach my $var1 (0, 1) {

  if( grep($var1, @arr1) ) {
        print "match $var1\n";
    }
  else {
    print "fail $var1\n";
  }

}
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nothing is returned when $var1 is 0 (false)

the entire list is returned when $var1 is 1 (true)

Update: Here's a sample usage:

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

my $paid = 0;  # :-(

my @shopping =
  (
   'twinkies','coffee',
   (grep !$paid => 'gruel', 'cabbage', 'cordial'),
   (grep $paid => 'caviar', 'truffles', 'champagne'),
  );

print "@shopping";
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