# firstname lastname age
joe builder 9
bob plumber 66
dora squarepants 10
diego simpson 11

##</code><code>##

open( $l, "<file" ) || die "Error : $!";
my @lines = <$l>;
close( $l );

foreach my $line ( @lines ) {
  
  # Skipping if the line is empty or a comment
  next if ( $line =~ /^\s*$/ );
  next if ( $line =~ /^\s*#/ );
  
  my ($firstname, $lastname, $age) = split( /\s+/, $line );
  
  # then do whatever you have to
}

##</code><code>##

# lastname firstname age gender phone
mcgee bobby 27 M 555-555-5555
kincaid marl 67 M 555-666-6666
hofhazards duke 22 M 555-696-6969

##</code><code>##

open( $l, "<file" ) || die "Error : $!";
my @lines = <$l>;
close( $l );

my @keys = split( /\s+/, $lines[0] );
shift( @keys ); # to remove the # as the first field

foreach my $line ( @lines ) {
  
  # Skipping if the line is empty or a comment
  next if ( $line =~ /^\s*$/ );
  next if ( $line =~ /^\s*#/ );
  
  my %hash;
  @hash{ @keys } = split( /\s+/, $line );
  
  # then do whatever you have to
}