open (FILE, shift);
my @file = <FILE>;

foreach $a (@file) {
   ...etc...
}

close (FILE);
[download]

my $name = shift or die "usage: $0 filename\n";
open FILE, '<', $name or die "Cannot open '$name' because: $!";
my ( $firstline, @file ) = <FILE>;
close FILE;

foreach my $line ( @file ) {
   ...etc...
}
[download]

OR:

my $name = shift or die "usage: $0 filename\n";
open FILE, '<', $name or die "Cannot open '$name' because: $!";
my $firstline = <FILE>;

while ( my $line = <FILE> ) {
   ...etc...
}

close FILE;
[download]

OR:

my $name = shift or die "usage: $0 filename\n";
open FILE, '<', $name or die "Cannot open '$name' because: $!";

my $firstline;
while ( my $line = <FILE> ) {
    if ( $. == 1 ) {
        $firstline = $line;
        next;
    }
   ...etc...
}

close FILE;
[download]