I was also confused by the wording of your problem and
what "element is non-empty" would mean. You also say that you don't
want repeated values, so a hash is idea for eliminating those. Sounds like
a fusion of
bichonfrise74 and
cdarke ideas is what you need.
#!/usr/bin/perl -w
use strict;
my %record;
while (my $line = <DATA>)
{
$line =~ s/\s+$//; #see [cdarke]'s comment, this
#also does chomp at same time
$record{$line}=1 if ( $line ne ""); #comparison allows "zero"
#$record{$line}++ if ( $line ne ""); #is also ok too. But I didn't
#think that you needed count
}
my @record = sort keys %record;
#sort keys %record is a list and can just be assigned to an
#array variable, which appears to be what you want as result.
#note that in Perl, the identifier "record" can be used both as
#an array(@record) and as a hash(%hash).
print "@record"; #prints: a b c d
__DATA__
a
b
c
d
a
a
c
d
c
