# Remove empty strings from @skeyw and @premiumkeyw
@skeyw = grep {$_ ne ""} @skeyw;
@premiumkeyw = grep {$_ ne ""} @premiumkeyw;

# Build a big regular expression out of @skeyw
# for faster matching.
my $skeyw_regexp = join('|', @skeyw);
$skeyw_regexp = qr/$skeyw_regexp/;

# Repeat for  @premiumkeyw
my $premium_regexp = join('|', @premiumkeyw);
$premium_regexp = qr/$premium_regexp/;

# Foreach line in @sidx
foreach my $line (@sidx) { 
        
        # Keep it (save it in @resultline) if it matches
        # any test in @skeyw.
        if($line =~ /$skeyw_regexp/) {
               
                # do something with search results

                push @resultline, $line;
                $icnt++;   # do you need this?
        }
}

# Foreach element in @sidx2
foreach my $line (@sidx2) { 

        # Keep it (save it in @resultline2) if it matches
        # any test in @premiumkey.
        if($line =~ /$premium_regexp/) {
               
                # do something with search results

                push @resultline2, $line;
                $icnt++;   # do you need this?
        }
}