#!/your/perl/here
use strict;
use warnings;
my $sequence;

while (my $line = <>)
{
  # Sequence keyword
  if ($line =~ /^Sequence:\s+(contig\d+)/)
  {
    $sequence = $1;  # save the sequence
    next;
  }

  # Parameter keyword
  next if ($line =~ /^Parameters:\s+(.*)$/);

  # print any other non-blank lines
  if ($line != /^\s*$/)
  {
    print "$sequence $line";
    next;
  }
}