#!/opt/local/bin/perl
use strict;
use warnings;

open my $vlan_in, '<', shift @ARGV;
my @vlans = <$vlan_in>;
foreach my $line (@vlans) {
  chomp $line;

  # Separate the 'vlan' from the list (and throw it away).
  my (undef, $vlans) = split /\s+/, $line;

  # Break up the list into items.
  my @items = split /,/, $vlans;

  # Print your new output.
  foreach my $item (@items) {
    next unless defined $item;
    $item =~ s/,//;
    print "vlan $item\n";
  }
}