Well, ++Albannach for not reading the whole file. But you could have saved some typing if we just want to print the first 10 lines:

    perl -pe '$.>10&&last' yourfile.txt
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However, the original poster might appreciate a little more verbosity and variation (and we'll get the lines into an array instead of just printing them):

# the Albannach method expanded (only read $n_lines from file):

    #!/usr/bin/perl -w
    use strict;
    my $n_lines = 10;
    my $file = 'blah';
    my @lines;
    open(FILE, $file)|| die "Can't $!";
    while(<FILE>){
        push @lines, $_;
        last if $. == $n_lines;
    }
    close FILE;
    print @lines;
    __END__

# A slight variation (only reads $n_lines):

    #!/usr/bin/perl -w
    use strict;
    my $n_lines = 10;
    my $file = 'blah';
    my @lines;
    open(FILE, $file)|| die "Can't $!";
    for (1 .. $n_lines) {
        push @lines, scalar <FILE>;
    }
    close FILE;
    print @lines;
    __END__

# let's read $n_lines one character at a time:

    #!/usr/bin/perl -w
    use strict;
    my $n_lines = 10;
    my $file = 'blah';
    $_ = '';
    open(FILE, $file)|| die "Can't $!";
    $_ .= getc(FILE) while tr/\n// < $n_lines;
    close FILE;
    my @lines = split/^/m;
    print @lines;
    __END__


# aww heck, lets read it all but only keep $n_lines:

    #!/usr/bin/perl -w
    use strict;
    my $n_lines = 10;
    my $file = 'blah';
    my @lines;
    open(FILE, $file)|| die "Can't $!";
    @lines[0..$n_lines-1] = <FILE>;
    close FILE;
    print @lines;
    __END__

# same idea, different implementation:

    #!/usr/bin/perl -w
    use strict;
    my $n_lines = 10;
    my $file = 'blah';
    open(FILE, $file)|| die "Can't $!";
    my @lines = (<FILE>)[0..$n_lines-1];
    close FILE;
    print @lines;
    __END__

# stand on someone else's shoulders (or head as the case may be):

    #!/usr/bin/perl -w
    use strict;
    my $n_lines = 10;
    my $file = 'blah';
    my @lines = `head -n$n_lines $file`;
    print @lines;
    __END__
[download]

so I was bored!