substr $scalar, 0, $n

Sounds like homework to me. If it's not I apologize. What have you tried? take a look at perlre or substring (<edit> duh.. substring rofl..you can emulate pop via a substitution which I had done recently and that was sticking in my head)</edit> if you haven't already.

substr, print substr $string, 0, $n;

printf("Segmentation fault\n");
sleep(4);
printf("just kidding. it's all good.\n");
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sub first_n_chars($$) {

        my $N = int shift;
        my $input = shift;
        my $output = "";

        for(;$N > 0; $N--) {
                $input =~ m/(.)/;
                $output .= $1;
        }
        return $output;
}

sub first_n_chars_2($$) {

        my $N = int shift;
        my $input = shift;

        my $dots = "";
        for(;$N > 0; $N--) { $dots .= '.'; }

        my $output = "";
        $input =~ m/($dots)/;
        $output .= $1;

        return $output;
}

sub first_n_chars_3($$) {

        my $N = int shift;
        my $input = shift;
        my $output = "";

        $input =~ m/(.{$N})/;
        $output = $1;

        return $output;
}

my $foo = "314159";
print "$foo\n";
print first_n_chars(1, $foo) , "\n";
print first_n_chars_2(2, $foo) , "\n";
print first_n_chars_3(3, $foo) , "\n";
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substr $scalar, 0, $n
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Start with a scalar that's n characters long and print it.

Note: Sorry, today's Friday and I just couldn't help it ;-P