use strict;
use warnings;

open my $fh, '<', $ARGV[0]
    or die "Cannot open file '$ARGV[0]' for reading: $!";

sub getsub
{
    my ($sub) = @_;
    print "inside sub for $sub\n";
    seek $fh, 0, 0;
    (/\.subckt $sub/ .. /\.ends/) && print while <$fh>;
}

my $line = <$fh>;

while ($line)
{
    if ($line =~ /^xa1/)
    {
        print "line found to be $line\n";
        my $next;
        $line =  $next while !eof && ($next = <$fh>) =~ /^\+/;
        $line =~ s/\s+$//;
        my $sub = (split /\s+/, $line)[-1];
        print "subcircuit found is $sub in $line\n";

        my $file_pos = tell $fh;
        getsub($sub);
        seek $fh, $file_pos, 0;

        $line = $next;
    }
    else
    {
        $line = <$fh>;
    }
}

close $fh
    or die "Cannot close file '$ARGV[0]': $!";