The usage of $_[0]


P

Peng Yu

I think that $_[0] should give me 'a' in the following example. But it
doesn't. Could you help understand why? How to get the first argument?

$ ./main.pl
ab
b

$ cat main.pl
#!/usr/bin/env perl

use strict;
use warnings;

sub mysub {
print @_, "\n";
print $_[0], print $_[1], "\n";
}

mysub 'a', 'b';
 
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R

RedGrittyBrick

I think that $_[0] should give me 'a' in the following example. But it
doesn't. Could you help understand why? How to get the first argument?

$ ./main.pl
ab
b

$ cat main.pl
#!/usr/bin/env perl

use strict;
use warnings;

sub mysub {
print @_, "\n";
print $_[0], print $_[1], "\n";

print $_[0], $_[1], "\n";
 
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P

Peter J. Holzer

I think that $_[0] should give me 'a' in the following example. But it
doesn't. Could you help understand why? How to get the first argument?

$ ./main.pl
ab
b

That's not true. Your program prints

ab <newline>
b <newline>
a1 <no newline here>

(The shell prompt may obscure the last line due to the missing newline,
but in any case there is no empty line after "b")

As an exercise, figure out why
print $_[0], print $_[1], "\n";
}

prints "b\na1".

hp
 

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