if i understand what you want, it's something like this:

note: i'm using the DATA filehandle for this example, just plug in your handle to work on real data. i assume you're reading in a record delimited by ".ENDS\n", then splitting on space, and pushing to arrays depending on the match. you don't want to push more than once per record.

correct me if i'm wrong.

 #!/usr/bin/perl -w
 use strict;
 $|++;


my(@PN, @GN);
$/ = ".ENDS\n";

my @a;
while( <DATA> )
{
    my %seen;
    local $\ = "\n";
    my @words = split / /, $_;
    for( @words )
    {
        if( /VDD|VCC/ )
        {
            print "Matched VDD $_\n";
            push @PN, $_ unless $seen{Power}++;
        }
        elsif( /VSS|GND/ )
        {
            print "Matched VSS $_\n";
            push @GN, $_ unless $seen{GND}++;
        }
    }
}
print scalar @PN, "\n", scalar @GN, "\n";

__DATA__
.SUBCKT FOO X y Z
.PININFO test VDD VDD VDD Vss vdd VSS t y foo
blah
blah
bla
.ENDS

.SUBCKT test2 vdds VSS VDD
.PININFO test2 2FS SEL
blah
blah
blah 
.ENDS
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