Compare Arrays and Delete Arrays - arrays

Question

I have below three sets ( arrays ) I need to perform an operation like this ( (A-B)UC ) on.
Can someone have the logic of this in Perl?
Here is my code I can able check for is B subset of A or not but I could not able to do "A-B":
my #array = (MAJOR,MINOR,MM,DD,YY);
my #exclude = (MM,MINOR,YY);
my #include = (LICENSE,VALID);
foreach (#exclude) {
if ( $_ ~~ #array ) {
print "\n $_ is defined in variables and it will be excluded \n";
#array = grep {!/\$_/} #array;
print "#array \n";
}
else {
print "\n $_ is not defined under variables please check the files \n";
exit 100;
}
}
foreach (#array){
print "$_ \n";
}
I suspect something is wrong in my logic with grep operation i.e. delete operation.

Answer 1

One problem with the grep is that $_ in the outer loop is redefined inside the grep block to each element of #array. You need to have different names. Also, your regex was lacking anchors; however, instead of a regex, just use string inequality. Try this:
my #array = qw(MAJOR MINOR MM DD YY);
my #exclude = qw(MM MINOR YY);
my #include = qw(LICENSE VALID);
foreach my $e (#exclude) {
if ( $e ~~ #array ) {
print "\n $e is defined in variables and it will be excluded \n";
#array = grep {$e ne $_} #array;
print "#array \n";
} else {
print "\n $e is not defined under variables please check the files \n";
exit 100;
}
}

Answer 2

use strict and warnings to alert you to many pitfalls in perl.
A hash is the most natural way to represent a set in perl.
use strict;
use warnings;
my #array = ('MAJOR','MINOR','MM','DD','YY');
my #exclude = ('MM','MINOR','YY');
my #include = ('LICENSE','VALID');
my %set;
# add #array to set
#set{#array} = ();
# remove #exclude
delete #set{#exclude};
# add #include
#set{#include} = ();
# array of elements resulting
my #result = sort keys %set;

Answer 3

You could use a set to do those kind of operations. I used a non-standard module Set::Scalar to help me with it:
#!/usr/bin/env perl
use warnings;
use strict;
use Set::Scalar;
my #array = qw(MAJOR MINOR MM DD YY);
my #exclude = qw(MM MINOR YY);
my #include = qw(LICENSE VALID);
my $array_set = Set::Scalar->new(#array);
my $exclude_set = Set::Scalar->new(#exclude);
my $include_set = Set::Scalar->new(#include);
my $result = $array_set->difference($exclude_set)->union($include_set);
use Data::Dumper;
print Dumper #$result;
Run it like:
perl script.pl
That yields:
$VAR1 = 'VALID';
$VAR2 = 'MAJOR';
$VAR3 = 'DD';
$VAR4 = 'LICENSE';